Ceramic-on-ceramic (CoC) total hip arthroplasty (THA) can produce articular noise during the normal activities, generating discomfort to the patient. THA noise has to be investigated also as a potential predictor and a clinical sign of prosthetic failure.

An observational study has been carried out to characterize the noise in CoC cementless THA, and to analyze the related factors. A total of 46 patients with noisy hip have been enrolled in 38 months, within the follow-up protocol normally applied for the early diagnosis of ceramic liner fracture [1]. Noise recording was based on a high-quality audible recorder (mod. LS 3, Olympus, Japan) and a portable ultrasonic transducer (mod USB AE 1ch, PAC, USA). The sensors for noise recording were applied to the hip of the patient during a sequence of repeatable motorial activities (forward and backward walking, squat, sit in a chair, flexion and extension of the leg). Sessions were also video-recorded to associate the noise emission to the specific movements.

Each noise event was initially identified by the operator and therefore classified by comparison to the spectral characteristics (duration, intensity and frequency) of the main noise types. Number and spectral characteristics of noise events were obtained and correlated to the factors describing the clinical status of the patient, the surgical approach, the prosthetic device implanted. The study investigated also the noise as a sign of implant failure, by comparison with the total number of implants failed in the cohort during the study.

We observed three types of noise with the main spectral characteristics in agreement to the literature: clicking, squeaking and popping. Among the identified types of noise, squeaking showed the longest duration and the highest amplitude. The 63% of hip presented the emission of just one type of noise, while the remaining a mix of types. The movement with the highest presence of noise was walking, followed by squat. Correlation was found between the noise type and the dimension of the ceramic head (p<0.001), with the sizes of 32 mm more affected by squeaking that the smaller one. Squeaking appeared before during the follow-up than the other types of noise. The 35% (16/46) of the noisy hips were revised during the study. Among the revised hips, the 81% (13/16) were affected by impingement and/or severe damage of the prosthetic components. The antiversion of the cup (p=0.008), the presence of debris in the synovial fluid (p=0.021) and the average frequency of squeaking (p=0.006) were significant predictors for the revision, but it has to be mentioned that the squeaking data was obtained on a small subset of revised patients. Ultrasonic analysis did not show significant correlations.

The study presented and validated an experimental procedure to analyze noisy hips in clinical trials. Noise is confirmed to be a significant parameter in the follow-up evaluation of ceramic THA.

After a few years from its introduction, the limits of the THA became evident, mainly due to high rates of mobilization for polyethylene wear and to the release of metal ions from MOM and MOP couplings.

Ceramic bearings were thus introduced in surgery to obtain lower levels of friction and wear.

These issues have now been well recognized by several studies, which show that ceramic-on-ceramic joint has the lowest wear rate among various articulations and that ceramic particles induce less macrophage reaction and decrease cytokine secretion, allowing to have little periprosthetic osteolysis.

After the first results in the late 70′s and early 80′s, the mechanical reliability was improved due to the manufacturers' efforts to reduce the ceramic fragility evolving average grain microstructure and lowering the degree of impurity.

Betterment and standardization of production have led to 3^rd generation alumina, Biolox Forte in 1994, that achieved a lower incidence of fracture.

The purpose of our study has been to assess long-term follow-up results of alumina-on-alumina 3^rd generation ceramic total hip cementless arthroplasty performed at our institution from January 1995 to December 2000.

We prospectively followed more than 200 patients operated of THA for primary or secondary hip osteoarthritis analyzing clinical and radiographs features.

In this period, the total hip replacement were performed by a single surgeon, who is the senior author (A.T.) in our Institution.

All patients were clinically examined to confirm the diagnosis and all of them were checked with a standard plain radiographs in two projections and, when necessary, the radiographic examination was completed by CT scans.

The same prosthesis was used in all patients, a 3^rd generation alumina COC articulation, composed of a hemispherical titanium alloy cup and a 28-mm alumina ceramic femoral head. The modular ceramic head was fixed to a 12/14 taper cone.

Proximally plasma-spray hydroxyapatite coated Ti alloy stems completes the implant features. Modular necks were used in retro or anteversion and varus or valgus offset, allowing changes in neck-shaft angle and giving a perfect intraoperative stability.

Clinical assessment was performed using the Merle-D'Aubigne and Postel hip score. Each patient was assessed before surgery, after 30 days, afterwards at 4 months and annually after surgery.

The mode of femoral component fixation was radiographically classified as bone ingrowth fixation, stable fibrous fixation or unstable fixation, according to the criteria Engh-Bobyn.

Osteolysis was evaluated on the femoral side at each Gruen zone. Osteolysis on the acetabular side was evaluated by DeLee and Chanley zone.

Our study has concluded that cementless modular hip arthroplasty with 3^rd generation ceramic-on-ceramic bearing, with a 13 to 18 years follow-up, shows an excellent survivorship, in particular for the very low volume release of microparticles during friction, which consequently reduction of cytokine release, thus diminishing the risk of periprosthetic osteolysis and loosening of implant components.

Aim: Polyethylene used for Total Hip Artrhroplasty components can be sterilized with different methods. Among them there is gamma rays. This method is currently used for conventional polyethylene and has been used also for Hylamer, a high cristallinity polyethylene manufactured by Depuy in early nineties. Recently Hylamer polyethylene components gamma sterilized in air were ‘recalled’ by Health Authorities, due to excessive wear. Aim of the present study was to evaluate radiographic and clinical performance of Hylamer acetabular liners gamma sterilized in air, and compare them to same devices gamma sterilized in nitrogen atmosphere.

Methods: Thirty-one patients “gamma in air” were matched to thirty controls with the same implanted socket but with the insert sterilized in a nitrogen atmosphere in a retrospective matched case-control. Moreover, a second control group was matched from twenty-three patients with a different prosthesis (ABG cup, Stryker-Howmedica) but with a similar insert made by conventional polyethylene gamma sterilized in absence of oxygen. Clinical evaluation was made according to the Harris Hip-scoring system. Radiographic wear measurements and osteolytic lesion was performed comparing the post-operative pelvic radiograph with the last follow-up study.

Results: Among 3 groups there was no significant difference in the clinical performance. At a mean of seven years, we found a significant difference between the mean rate of wear and osteolytic lesion of Hylamer sterilized in air and Hylamer sterilized in a nitrogen atmosphere.

Conclusion: We concluded that the manufacturing and sterilization processes influence the resistance to oxidation and wear of the various types of ultra-high molecular polyethylene that are currently available.