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Level I, prospective randomized controlled trial.

PurposeThe theoretical advantages of mobile-bearing (MB) designs over the conventional fixed bearings (FBs) for total knee arthroplasty (TKA) have not been proved yet through clinical studies. The aim of the study was to test whether the MB design has advantages in terms of better clinical outcomes when compared to FB. Furthermore, the relationships between intra-operative obtained implant positioning data and the clinical scores were analysed.MethodsA total of 99 patients were randomized into the FB or the MB group. All patients received the same posterior cruciate retaining implants and were operated with the use of a computer-assisted navigation system. The clinical outcomes of both groups were compared pre-operatively, at 1 year, and at a mean follow-up time of 4 years after surgery.ResultsThe MB implants showed no advantages over the FB when comparing the Knee Society Scores, the Oxford Score, the range of movement (ROM) and pain intensity of the patients in both groups at 1 and 4 years after surgery. There were no relationships between the computer navigation data and the clinical scores.ConclusionsIn view of the 4-year results, there is no evidence to support the recommendation of one design over the other in terms of better clinical outcome scores, higher ROM or lower pain rates. Long-term follow-up results may be necessary, including survival rates. Further research comparing different TKA designs should also include standardized performance-based tests.Level of evidenceProspective study (Randomized controlled trial with adequate statistical power to detect differences), Level I.

No abstract

Abstract. Owing to an ageing population, the impact of unhealthy lifestyle, or simply congenital or gender specific issues (dysplasia), degenerative bone and joint disease (osteoarthritis) at the hip pose an increasing problem in many countries. Osteoarthritis is painful and causes mobility restrictions; amelioration is often only achieved by replacing the complete hip joint in a total hip arthroplasty (THA). Despite significant orthopaedic progress related to THA, the success of the surgical process relies heavily on the judgement, experience, skills and techniques used of the surgeon. One common way of implanting the stem into the femur is press fitting uncemented stem designs into a prepared cavity. By using a range of compaction broaches, which are impacted into the femur, the cavity for the implant is formed. However, the surgeon decides whether to change the size of the broach, how hard and fast it is impacted or when to stop the excavation process, merely based on acoustic, haptic or visual cues which are subjective. It is known that non-ideal cavity preparations increase the risk of peri-prosthetic fractures especially in elderly people. This study reports on a simulated hip replacement surgery on a cadaver and the analysis of impaction forces and the microphone signals during compaction. The recorded transient signals of impaction forces and acoustic pressures (≈ 80 µs -2 ms) are statistically analysed for their trend, which shows increasing heteroscedasticity in the force-pressure relationship between broach sizes. TIKHONOV regularisation, as inverse deconvolution technique, is applied to calculate the acoustic transfer functions from the acoustic responses and their mechanical impacts. The extracted spectra highlight that system characteristics altered during the cavity preparation process: in the high-frequency range the number of resonances increased with impacts and broach size. By applying nonlinear time series analysis the system dynamics increase in complexity and demand for a larger minimum embedding dimension. The growing number of resonances with similar level of the transfer function indicates a higher propensity to dissipate energy over sound; the change in embedding dimension indicates a decrease in linearity. The spectral changes as well as the altered dimension requirements indicate either an improved coupling between the bone and the broach or the onset of micro-fractures caused by growing stress levels within the bone.

The intra-rater reliability values achieved were suitable. Intraclass correlation coefficient values for inter-rater reliability remained below an acceptable level. Possible reasons and overcoming strategies were presented. The 95% limits of agreement were good, at less than ±2°.

Background:The mobile bearing designs have not yet been shown to improve clinical outcome of total knee arthroplasty (TKA). In this prospective randomized study, we compared the short-term clinical results of a mobile bearing implant with those of the fixed bearing version of the same implant.Methods:We randomized 100 knees into two double-blind groups who received either the fixed (FB, 52 knees) or the mobile bearing (MB, 48 knees) version of the same implant. We used navigation to standardize the surgical technique. For up to one year, we recorded the Knee Society (KSS) and Oxford (OXF) scores. We performed an exploratory analysis of variance (ANOVA) to determine the influence of baseline scores as covariate and the extent of improvement in clinical outcome over time.Results:After one year, we did not detect any statistically significant difference between the two groups. The KSS scores differed by 2 points, the OXF scores by 1.1 points.Conclusion:Even with identical geometry of implant surfaces and a navigated surgical technique, first-year results do not support a preference for either a fixed or a mobile design.

Background The influence of the surgical process on implant loosening and periprosthetic fractures (PPF) as major complications in uncemented total hip arthroplasty (THA) has rarely been studied because of the difficulty in quantification. Meanwhile, registry analyses have clearly shown a decrease in complications with increasing experience. The goal of this study was to determine the extent of variability in THA stem implantation between highly experienced surgeons with respect to implant size, position, press-fit, contact area, primary stability, and the effect of using a powered impaction tool. Methods Primary hip stems were implanted in 16 cadaveric femur pairs by three experienced surgeons using manual and powered impaction. Quantitative CTs were taken before and after each process step, and stem tilt, canal-fill-ratio, press-fit, and contact determined. Eleven femur pairs were additionally tested for primary stability under cyclic loading conditions. Results Manual impactions led to higher variations in press-fit and contact area between the surgeons than powered impactions. Stem tilt and implant sizing varied between surgeons but not between impaction methods. Larger stems exhibited less micromotion than smaller stems. Conclusions Larger implants may increase PPF risk, while smaller implants reduce primary stability. The reduced variation for powered impactions indicates that appropriate measures may promote a more standardized process. The variations between these experienced surgeons may represent an acceptable range for this specific stem design. Variability in the implantation process warrants further investigations since certain deviations, for example, a stem tilt toward varus, might increase bone stresses and PPF risk.