Aim

Periprosthetic joint infections (PJI) are severe complications after total joint arthroplasty (TJA). Up to now, a gold standard in the diagnostics of PJI is missing. Small extracellular vesicles (sEVs) are secreted by all types of cells and play a key role in immune response in presence of infection (1).

In this prospective study, the diagnostic accuracy of sEVs in the synovial fluid to detect PJI of knee, hip and shoulder joints was investigated. We hypothesized increased surface markers of sEVs in PJI compared to aseptic complications (e.g. implant loosening, stress shielding related pain).

Our understanding of the origin of hip pain in degenerative disorders of the hip, including primary osteoarthritis, avascular necrosis and femoroacetabular impingement (FAI), is limited. We undertook a histological investigation of the nociceptive innervation of the acetabular labrum, ligamentum teres and capsule of the hip, in order to prove pain- and proprioceptive-associated marker expression. These structures were isolated from 57 patients who had undergone elective hip surgery (44 labral samples, 33 ligamentum teres specimens, 34 capsular samples; in 19 patients all three structures were harvested). A total of 15 000 histological sections were prepared that were investigated immunohistochemically for the presence of protein S-100, 68 kDa neurofilament, neuropeptide Y, nociceptin and substance P. The tissues were evaluated in six representative areas.

Within the labrum, pain-associated free nerve ending expression was located predominantly at its base, decreasing in the periphery. In contrast, the distribution within the ligamentum teres showed a high local concentration in the centre. The hip capsule had an almost homogeneous marker expression in all investigated areas.

This study showed characteristic distribution profiles of nociceptive and pain-related nerve fibres, which may help in understanding the origin of hip pain.

Cite this article: Bone Joint J 2013;95-B:770–6.

Introduction: The use of screw fixation for cementless porous-coated acetabular components for primary total hip arthroplasty (THA) remains controversial. Aim of this study was to evaluate initial acetabular implant stability and late acetabular implant migration with screw fixation of the acetabular component in order to answer the question whether screws are necessary for the fixation of the acetabular component in cementless primary THA.

Methods: In a prospective study, 102 patients (107 hips) were available for follow up after primary THA using a cementless, porous-coated acetabular component. Patients were followed up at 6 and 12 weeks, 6 and 12 months and annually thereafter to an average of 2.6 ± 1.7 years. A total of 428 standardized radiographs were analyzed by the Einzel-Bild-Röntgen-Analyse (EBRA)-digital method. Additionally, the Harris Hip Score (HHS, 0–100) was assessed at the latest follow-up.

Results: 101 (94.4 %) implants did not show significant migration of more than 1 mm of the acetabular component. Six (5.6%) implants showed a migration of more than 1 mm: in 3 cases (2.8%), migration was progressive during follow-up and led to a revision surgery due to aseptic loosening. In 3 cases, migration came to a halt and cups were claimed stable. Individuals without cup migration had an average HHS of 78.4 ± 22.9, whereas patients who showed a cup migration of > 1 mm had 53.3 ± 24.2. Statistical analysis did not reveal preoperative patterns that would identify future migration.

Discussion: and Conclusion: Our findings show that the use of screw fixation for cementless porous-coated acetabular components for primary THA does not prevent cup migration.

Introduction: Femoroacetabular Impingement (FAI) with more or less subtle abnormality of the hip anatomy and function may contribute to the early development of osteoarthritis (OA). Surgical dislocation as well as arthroscopy of the hip joint are effective and save tools to correct these anatomic deformities. Good clinical results could be achieved predominantly in patients not exceeding grade I OA. The aim of the presented study was to evaluate the clinical and radiological outcome of patients that were treated by open surgical hip dislocation for more advanced OA of the hip joint (> grade I).

Patients and Methods: This is a prospective clinical trial on the outcome of patients after surgical hip dislocation. We report on 45 hip joints (41 patients, 16 m, 25 f) that were treated in our institution by offset-correction (removal of osseous bumps at the femoral head-neck junction) and/or labral surgery for FAI. All patients were evaluated prospectively before and after surgery (Harris Hip Score, radiographic parameters, arthro-MRI).

Results: The mean follow up (FU) was 45 months (range: 12–102 months). 9 hips underwent total hip replacement in the further course of FU for persisting pain. In the remaining hips a significant pain reduction but no amelioration of hip range of motion could be accomplished. In 90% of the cases, a good correlation between preop-erative arthro-MRT findings and intraoperative labrum and cartilage assessment could be demonstrated. Concerning the outcome, no patient or radiographic factors could be identified that were strongly associated with failure after surgical dislocation.

Discussion and Conclusion: Our data suggests that even patients with more advanced osteoarthritis of the hip may benefit from the surgical dislocation approach as a hip salvage procedure. However, the high number of conversion to total hip arthroplasty indicates, that the indication for hip salvage should stay restricted. Patient or radiographic factors indicative of failure could not be identified. In the future and with more sophisticated molecular MRI techniques such as delayed Gadolinium Enhanced MRI of Cartilage (dGEMRIC) concrete prediction models could be implemented to preoperatively assess hip cartilage in order to sort out patients who will not profit from salvage surgery for advanced OA due to FAI.