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.

In clinical orthopedics suitable materials that induce and restore biological functions together with the right mechanical properties are particularly needed for the regeneration of musculoskeletal tissue. An innovative solution to answer this need is represented by tissue engineering. This technique could overcome the limits of traditional approaches involving the use of homologous, autologous or allogenetic tissue (e.g. tissue availability, immune rejection and pathogen transfer). In this field, rapid prototyping techniques are emerging as the most promising tool to realize three-dimensional tissue constructs with highly complex geometries.

Based on CAD/CAM technology, rapid prototyping allows development of patient-specific 3D scaffolds from digital data obtained with latest generation imaging tools. These structures can be realized in different materials, tailoring their mechanical properties and architectural features. Most rapid prototyping techniques allow the creation of acellular 3D scaffolds, which must be subsequently seeded with cells. Conversely, 3D bioprinting can deposit bio-ink containing molecules/cells, providing desired spatial distribution of growth factors/cells within the scaffold. The need of printable materials suitable for processing with inkjet, dispensing, or laser-print technologies, forces the use of matrices within a specific range of viscosity. However, these materials have low mechanical features. To overcome this problem and to obtain a final construct with good mechanical properties, bioprinting tissue fabrication can rely on the alternate deposition of thermoplastic materials and cell-laden hydrogels. Since mechanical performance is determined not only by the material properties but also by the geometry (microarchitecture) of the structure, printing parameters can be modified to obtain the desired features.

The new 3D platform available at Rizzoli Orthopaedic Institute, consisting of a Computer Tomography (GE Medical Systems, Milano, Italia) and a 3D Bio-Printer (RegenHU, Villaz-St-Pierre, Switzerland) is used to address the above-mentioned issues. Preliminary results showed that it is possible to modify the microarchitecture of the printed structures adjusting their apparent density and stiffness in the range of the trabecular bone tissue. Additionally, it has been proven that the calcium phosphate based paste, used as bioink, allows cell attachment and proliferation. Therefore, the platform allows to print scaffolds with open and interconnected porosities and suitable mechanical properties. They can be filled with different components such as cells or soluble growth factors at specific locations.