Dissociation of liner from cup in THA: does liner damage affect the risk of dissociation?

INTRODUCTION: A rare catastrophic failure of modular component Total Hip Arthroplasty is dissociation between liner and cup, which has been associated with component malposition and/or impingement and seems to be more frequently associated with the Pinnacle system. The goal of this study was to evaluate the resistance of a polyethylene liner to lever-out-forces of the Pinnacle locking mechanism and the locking mechanisms of two other current cup/liner systems using a standardized testing method (ASTM). MATERIALS AND METHODS: Five of each of the following cups were evaluated with their corresponding polyethylene liners: Pinnacle Multihole cup with and without intact anti-rotation tabs (ART's); Allofit-S-Alloclassic and Plasmafit Plus7 cups. The ASTM test set-up was used to evaluate the lever-out force resulting in liner dissociation for each construct. RESULTS: The Pinnacle construct with intact ARTs required the greatest force (F) to achieve dissociation (263.2 ± 79.2 N) followed by the Plasmafit Plus7 (185.8 ± 36.9 N) and the Allofit-S (101.4 ± 35.3 N) constructs, respectively. However, after removal of the ARTs, the Pinnacle system required the least force to achieve dissociation (75.1 ± 22.2 N) (p < 0.001). CONCLUSIONS: The intact Pinnacle system appeared the most stable in lever-out tests when compared to the other systems. However, after removal of the ARTs, the Pinnacle system required the least force for dissociation, consistent with locking mechanism failure, and suggesting that the ARTs are a critical component of the locking mechanism. Our findings are consistent with the clinical experience of dissociated Pinnacle constructs displaying damaged or missing ARTs, and that damage to these may increase risk of liner dissociation.

The Top Three Burning Questions in Total Hip Arthroplasty.

Total hip arthroplasty (THA) for end-stage osteoarthritis is one of the most effective surgical treatments in medicine. Impressive outcomes have been well documented in the literature with patients gaining ambulation and recovery of hip joint function. Nevertheless, there are still debatable issues and controversies that the orthopedic community has not been able to provide a definitive answer for. This review is focused on the current three most debatable issues surrounding the THA procedure: (1) new cutting-edge technology, (2) spinopelvic mobility, and (3) fast-track protocols. The scope of the herein narrative review is to analyze the debatable issues surrounding the three aforementioned topics and conclude the best contemporary clinical approaches regarding each issue.

Outcome Prognostic Factors in MRI during Spica Cast Therapy Treating Developmental Hip Dysplasia with Midterm Follow-Up.

Closed reduction followed by spica casting is a conservative treatment for developmental dysplasia of the hip (DDH). Magnetic resonance imaging (MRI) can verify proper closed reduction of the dysplastic hip. Our aim was to find prognostic factors in the first MRI to predict the possible outcome of the initial treatment success by means of ultrasound monitoring according to Graf and the further development of the hip dysplasia or risk of recurrence in the radiological follow-up examinations. A total of 48 patients (96 hips) with DDH on at least one side, and who were treated with closed reduction and spica cast were included in this retrospective cohort study. Treatment began at a mean age of 9.9 weeks. The children were followed for 47.4 months on average. We performed closed reduction and spica casting under general balanced anaesthesia. This was directly followed by MRI to control the position/reduction of the femoral head without anaesthesia. The following parameters were measured in the MRI: hip abduction angle, coronal, anterior and posterior bony axial acetabular angles and pelvic width. A Graf alpha angle of at least 60° was considered successful. In the radiological follow-up controls, we evaluated for residual dysplasia or recurrence. In our cohort, we only found the abduction angle to be an influencing factor for improvement of the DDH. No other prognostic factors in MRI measurements, such as gender, age at time of the first spica cast, or treatment involving overhead extension were found to be predictive of mid-term outcomes. This may, however, be due to the relatively small number of treatment failures.

Application of the reversed LISS-DF technique in an elderly patient to salvage infection-related failure of trochanteric fracture fixation.

Failure of cephalomedullary fixation in geriatric trochanteric fractures is a potential complication. Attempts have been made to optimize the implant fixation (e. g. cement augmentation) and several factors (e. g. malreduction, tip apex distance) have been identified as risk factors for failure. Nevertheless, if intramedullary fixation fails, it is often associated with bone defects in mostly preexisting poor bone-stock. Accordingly, conversion to total hip arthroplasty (THA) is recommended by some authors as the only valid treatment option. However, in specific situations (e. g. implant associated infection) conversion to THA might be less reasonable than an attempt to re-osteosynthesis. This article reports on the successful use of a reversed contralateral LISS-DF (LISS for the distal femur, DePuy Synthes, Zuchwil, Switzerland) application after failed cephalomedullary fixation and failed re-osteosynthesis using a blade plate in a trochanteric fracture in an elderly patient with additional implant associated infection.