Impingement Between the Metal Stem and the Ceramic Liner in Total Hip Arthroplasty: The Neck Is Not the Only Place Where Impingement Occurs

Quarter Century Outcomes of Alumina Ceramic-on-Ceramic Total Hip Arthroplasty

BACKGROUND

Alumina ceramic-on-ceramic (CoC) bearings were widely used in total hip arthroplasty (THA) due to their superior wear resistance and inert properties, making them ideal for young, active patients who require long-lasting implants. This study aimed to synthesize findings from previous reports, providing a comprehensive follow-up of at least 25 years on the clinical and radiologic outcomes, the prevalence of osteolysis, and implant survivorship in patients undergoing primary cementless CoC THA.

METHODS

We have previously reported 5- to 10-year outcomes following the implementation of third-generation alumina-on-alumina bearings in a consecutive series of 100 primary cementless THAs. This report updates those results with a minimum follow-up of 25 years. Of the original cohort, 58 patients who had 67 hips were available for the latest follow-up. Clinical assessments were performed using the Harris Hip Score and pain questionnaires. Radiographic evaluations were employed to assess implant fixation and osteolysis.

RESULTS

At the final follow-up, the implant survival rate was an impressive 96.3%, with revision of the implant as the end point. The mean Harris Hip Score improved significantly from preoperative values to 90.1, indicating excellent functional outcomes. The incidence of ceramic-related noise increased over time, with three cases of ceramic head fractures requiring a change of bearings. Notably, the extent of stem notching observed in earlier reports did not show further progression. Radiologically, all implants demonstrated bony ingrowth with no signs of aseptic loosening or major osteolysis.

CONCLUSIONS

The long-term (minimum 25-year) follow-up of alumina-on-alumina bearings in primary cementless THA demonstrates outstanding implant survivorship, excellent functional outcomes, and minimal adverse effects over 25 years. Despite some issues like ceramic-related noise and component fractures, the overall performance of CoC bearings remains highly encouraging, particularly suitable for young, active patients. Surgeons should provide appropriate education to both potential THA candidates and patients who already have THAs with CoC bearings.

LEVEL OF EVIDENCE

Therapeutic Level IV.

Total Hip Arthroplasty with Extra-small Femoral Stems in Extremely Hypoplastic Femurs: A Case-Series Study

Background

Total hip arthroplasty (THA) in patients with hypoplastic femurs presents a significant challenge to orthopedic surgeons due to the limited space available for implant placement. Therefore, the extra-small femoral stems have been proposed as a solution to this problem, but there are limited data on the outcomes. We aimed to evaluate clinical and radiological outcomes of THA in patients with extremely hypoplastic femurs using the Bencox CM stem (Corentec), an extra-small femoral stem.

Methods

We included 6 hips from 4 patients. The mean age of the patients was 41.2 years (range, 19.6-60.4 years). The mean height was 135.1 cm (range, 113.6-150.0 cm) with a mean body mass index of 25.7 kg/m2 (range, 21.3-31.1 kg/m2). The diagnoses for THA were sequelae of septic arthritis in childhood, pseudoachondroplasia, spondyloepiphyseal dysplasia, and juvenile rheumatoid arthritis. Preoperative computed tomography scans were conducted to assess the extent of proximal femoral hypoplasia. The clinical outcomes were assessed using the modified Harris Hip Score, while the radiological outcomes were evaluated using radiographs. The mean follow-up was 2.3 years (range, 1.0-5.9 years).

Results

The average modified Harris Hip Score improved to 88.8 at the final follow-up. Intraoperative femoral fractures occurred in 2 cases (33.3%). During the follow-up, 1 stem underwent varus tilting from postoperative 6 weeks to 6 months without subsidence. Otherwise, all stems showed good osteointegration at the latest follow-up. No hip dislocations, periprosthetic joint infection, or loosening of the prosthesis occurred.

Conclusions

The use of extra-small femoral stems in THA for extremely hypoplastic femurs can provide reasonable clinical and radiological outcomes with minimal complications. We suggest that this femoral stem could be a viable option for patients with extremely hypoplastic femurs.

Computed Tomography Evaluation of Alumina Ceramic-on-Ceramic Total Hip Arthroplasty With More Than 20 years of Follow-Up: Is a Follow-Up Computed Tomography Scan Necessary?

BACKGROUND

Ceramic-on-ceramic (CoC) bearings have been increasingly used in total hip arthroplasty (THA) because of their superior wear resistance and biocompatibility. However, there is a scarcity of reports on the computed tomography (CT) evaluation of CoC bearings with more than 10 years. The aim of this study was to evaluate the long-term CT results of THA using CoC bearings for more than 20 years of follow-up. We hypothesized that there would be no wear, osteolysis, or ceramic fracture.

METHODS

Between November 1997 and June 2003, 956 hips underwent THA using alumina-on-alumina bearings at a tertiary referral hospital. Among them, 107 hips were assessed, all of which underwent a CT examination more than 20 years after the index surgery. The mean age at the time of surgery was 41 years, and a CT scan was performed at an average of 22.0 years postoperatively (range, 20.0 to 25.1). The CT scans were thoroughly assessed for osteolysis, stem notching, and ceramic component fracture.

RESULTS

No loosening was observed in the acetabular cup or femoral stem. Stem notching was observed in 3 hips (2.8%). In the CT scan taken after a minimum of 20 years of follow-up, 1 case (0.9%) of osteolysis around the cup and 2 cases (1.9%) of osteolysis around the femoral stem were noted. Suspected chip fractures of the ceramic insert were discovered in 4 cases (3.7%). Despite these findings, the patients remained asymptomatic, and no subsequent surgical intervention was needed after close follow-up.

CONCLUSIONS

Routine CT examinations for patients who underwent THA using CoC bearings over 20 years ago revealed unexpected findings, such as osteolysis and suspected chip fractures of the ceramic liner. However, routine CT scans may not be universally necessary. The CT evaluation in this cohort should be selectively performed for patients who have relevant clinical symptoms.

LEVEL OF EVIDENCE

Level III, Therapeutic study.

Ceramic-on-Ceramic or Metal-on-Polyethylene: The Bearing of Choice after Ceramic Component Fracture in Total Hip Arthroplasty along with Concise Follow-Up of the Previous Cohort

OBJECTIVE

We previously reported the questionable result of reoperation using metal-on-polyethylene (MoP) bearing after the fracture of the ceramic component. After the report, we abandoned the use of MoP; instead, we used ceramic-on-ceramic (CoC) bearing. This report aimed to present the outcome of reoperation to CoC bearing after ceramic component failures along with the longer-term outcome of the previously reported cohort with an MoP bearing.

RESULTS

The mean follow-up of the MoP cohort was extended from 4.3 years to 8.8 years. Metallosis had occurred in three of nine patients of the previous cohort, which all required re-reoperations. Two hips from 11 patients with revision to CoC had re-reoperations due to ceramic liner fracture and non-union of the osteotomized fragment, respectively. No metallosis and wear occurred in the cohort revised with CoC articulation. Otherwise, there were no adverse changes in radiographs and no impairment in functions.

METHODS

We conducted an extended prospective evaluation of a previous cohort consisting of six head fractures and three liner fractures. In this cohort, the patients underwent a bearing change to metal-on-polyethylene. Additionally, we retrospectively analyzed 11 cases of third-generation ceramic bearing fractures, comprising nine head fractures and two liner fractures. These cases were subsequently treated with a bearing change to fourth-generation CoC. We assessed clinical and radiological outcomes, including complication rates, in both groups.

CONCLUSION

We recommend the latest CoC as the bearing of choice in reoperation after the fracture of ceramic components. In the case of an MoP bearing after the ceramic component fracture, the risk of metallosis seemed high in the early postoperative period.

Damage analysis of retrieved BioloxⓇdelta components used in hard and soft bearings

This retrieval study included 43 Biolox delta explants (18 CoC, 25 CoP). Implants were examined macroscopically, whereby damage was evaluated using a semi quantitative scoring system. Confocal microscopy was used to examine wear related damage patterns of the articulating surfaces. Scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) was used to analyze wear marks on the implant surface and wear debris in periprosthetic tissue samples. Raman spectroscopy and X-ray diffraction (XRD) were used to quantify monoclinic zirconia fractions. On all components, in vivo wear resulted predominantly in different damage patterns caused by metal transfer. In CoC bearings stripe wear was additionally detected, and some implants underwent severe damage due to component breakage. The wear scores were higher for CoC components, with no differences between the scores for CoC heads and liners. Wear features caused comparable roughening on implants from CoC and CoP bearings. SEM studies demonstrated that most wear marks were caused by metal debris released from implant components. Grain pull-out was observed in stripe wear regions. Monoclinic phase shift was observed in a similar quantity on components from CoP and CoC bearings. The increase of monoclinic zirconia content around metal deposits was minimal and was more pronounced in areas of stripe wear. The results of this study indicate, that ZTA components in general undergo minimal wear in both, CoC and CoP bearings, however, it is more pronounced in the former. Metal deposits, as the most common wear feature, have no significant effect on monoclinic phase transition. STATEMENT OF SIGNIFICANCE: In this paper, we classify all damage patterns macroscopically according to an established scoring system and assess them regarding surface roughness (confocal microscopy) and monoclinic phase content (Raman spectroscopy) in order to derive the severity for patients. We compare hard-hard and hard-soft bearings and relate damage patterns with metal transfer based on SEM/EDS examinations. Furthermore, we work out correlations between patient-specific data, cause of revision and the physical condition of each individual sample Our cohort consists of 43 Biolox delta retrievals, a comparatively large quantity. In addition, we address current topics such as metal transfer and, based on the classification of damage patterns, provide incentives and/or meaningful focal points for further research.

High Risk of Neck-liner Impingement and Notching Observed with Thick Femoral Neck Implants in Ceramic-on-ceramic THA

BACKGROUND

Recently, impingement between the femoral stem and ceramic liner, which appears as a notch in the stem neck on radiographs, has emerged as a new complication. However, the proportion of impingement, potential risk factors, and related complications are poorly elucidated.

QUESTION/PURPOSES

In patients who underwent ceramic-on-ceramic (CoC) THA and had at least 10 years of follow-up, we asked: (1) What proportion had radiographic evidence of stem neck-ceramic liner impingement (notching of the stem), and what implant design, implantation factors, or complications such as ceramic fracture or metallosis are associated with impingement? (2) How common are the complications of noise and ceramic fracture? (3) What are the radiologic changes (including fixation of femoral and acetabular components, osteolysis, and heterotopic ossification) and clinical outcomes as determined by the modified Harris hip score (mHHS) for this cohort? (4) What is the survivorship with implant revision as the endpoint and with reoperation for any reason as the endpoint after CoC THA using a thick-neck stem design?

METHODS

Between May 2003 and April 2010, 643 patients underwent primary THA at a tertiary referral hospital. After excluding patients with metal-on-polyethylene and with ceramic-on-polyethylene implants, 621 patients were considered eligible for this study. All patients received the same hemispherical titanium cup, a standard-length tapered titanium stem, and a CoC bearing. Of those, 19% (115) were lost to follow-up before 10 years, and 8% (50) were excluded because they died before the minimum follow-up duration of 10 years, leaving 73% (456) for analysis. Patients had a mean age of 50 ± 14 years and were followed for a median (range) of 13 years (10 to 17). The mean cup abduction was 38° ± 5°, and the mean cup anteversion was 26° ± 7°. To determine the proportion of patients with the neck-liner impingement, we analyzed the plain radiographs of every patient during follow-up to detect notches around the stem. The detection of stem neck notches on the radiographs was reliable (intraobserver reliability: κ = 0.963; p < 0.001 and interobserver reliability: κ = 0.975; p < 0.001). To evaluate factors related to notching, we compared the possible confounding factors including gender, age, BMI, implant position, neck length, and head diameter. Complications such as ceramic fracture, noise, dislocation, and periprosthetic joint infection were recorded. Noise was evaluated via interview and with the Hip Noise Assessment Questionnaire, which assessed the noise qualitatively. For clinical outcome, we assessed the mHHS, which includes pain and function scales (0 [worst] to 100 [best]), every visit. Tilting of at least 4° or migration of at least 4 mm was the criteria for cup loosening; subsidence more than 3 mm, any change in position, or a continuous radiolucent line greater than 2 mm was the criteria for stem loosening. To evaluate osteolysis, we performed CT scans in 57% (262 of 456) of patients. Kaplan-Meier survivorship analysis was performed using the endpoints of survivorship free from implant revision and survivorship free from reoperation for any cause.

RESULTS

The proportion of stem neck notching was 11% (49 of 456). There were no differences in cup abduction and anteversion between hips with notches and those without notches. Notched hips were more likely to have 28-mm than 32-mm heads (90% [44 of 49] versus 70% [285 of 407]; odds ratio 3.77 [95% CI 1.46 to 9.73]; p = 0.004). None of the 49 notched hips had a ceramic head or liner fracture or evidence of metallosis. A ceramic head fracture was reported in 2% (9 of 456); all fractures occurred in 28-mm short neck heads. A ceramic liner fracture occurred in 0.2% (1 of 456), and noise was noted in 6% (27 of 456). Acetabular osteolysis developed in 2% (7 of 456). The mHHS was 91 ± 12 points at the final follow-up. The survivorship free from implant revision was 97% (95% CI 96% to 99%), and the survivorship free from reoperation for any cause was 96% (95% CI 95% to 98%) at 13 years.

CONCLUSION

The proportion of stems with neck-ceramic liner impingement and ceramic component fracture were unacceptably high after the use of a thick-neck stem design, especially when a 28-mm head was used. We have discontinued the use of this stem design and we recommend that such stems should not be used when CoC bearings are used. As these findings might be generalized to other bearing couples, further studies focused on polyethylene liner wear and local metallosis due to thick stem neck are warranted.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Total Hip Arthroplasty Performed with a Novel Design Type 1 Femoral Stem: A Retrospective Minimum 5-Year Follow-up Study

Background

The Bencox M stem is a mid-short type 1 stem with additional unique design features. It has a reduced stem length and a lateral shoulder to facilitate minimally invasive surgery, as well as an angular lateral shoulder and a trapezoidal neck to minimize stem-liner impingement. There have been many mid-term reports on type 1 stems, but no results have been reported so far on this novel design type 1 femoral stem. This study presents the clinical and radiological outcomes of total hip arthroplasty performed with the M stem after a minimum 5-year follow-up.

Methods

From July 2014 to February 2015, 125 primary total hip arthroplasties using the M cementless femoral stem were performed on 112 patients in our hospital. Among them, 94 patients (106 hips) were eligible for the study and were followed up for more than 5 years. Our primary outcome was clinical results, which were evaluated by the Harris Hip Score (HHS), thigh pain, noise, and other complications. Secondary outcome was radiological outcomes. Seventy-seven hips were evaluated radiologically with attention to implant fixation, migration, loosening of component, degree of stress shielding, radiolucent lines, focal osteolysis, heterotopic ossification, and the evidence of impingement between the stem and liner.

Results

The average HHS improved from 54.6 points (range, 24–67 points) to 96.8 points (range, 91–100 points) at the latest follow-up. Three hips (2.8%) had intermittent thigh pain, which was tolerable without medication. Five hips (4.7%) had ceramic-related noise. There were no other complications such as infection, nerve injury, dislocation, or revision. All implants showed radiographic evidence of stable fixation by bone ingrowth without migration. Fifty-seven hips (74%) showed mild femoral stress shielding. Distal cortical hypertrophy was detected in 7 hips (9%), and heterotopic ossification was observed in 17 hips (22%). No implant demonstrated focal osteolysis and notching of the femoral neck or shoulder on radiographs.

Conclusions

The minimum 5-year results of total hip arthroplasty performed with the M cementless femoral stem were encouraging clinically and radiologically. A long-term follow-up will be necessary to evaluate its longevity.