Biomechanical phenomena occurring at the bone–implant interface during the press-fit insertion of acetabular cup implants are still poorly understood. This article presents a nonlinear geometrical two-dimensional axisymmetric finite element model aiming at describing the biomechanical behavior of the acetabular cup implant as a function of the bone Young’s modulus Eb, the diametric interference fit ( IF), and the friction coefficient µ. The numerical model was compared with experimental results obtained from an in vitro test, which allows to determine a reference configuration with the parameter set: μ*  = 0.3, [Formula: see text], and IF*  = 1 mm for which the maximal contact pressure tN = 10.7 MPa was found to be localized at the peri-equatorial rim of the acetabular cavity. Parametric studies were carried out, showing that an optimal value of the pull-out force can be defined as a function of μ, Eb, and IF. For the reference configuration, the optimal pull-out force is obtained for μ  = 0.6 (respectively, Eb = 0.35 GPa and IF = 1.4 mm). For relatively low value of µ ( µ < 0.2), the optimal value of IF linearly increases as a function of µ independently of Eb, while for µ > 0.2, the optimal value of IF has a nonlinear dependence on µ and decreases as a function of Eb. The results can be used to help surgeons determine the optimal value of IF in a patient specific manner.

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Among the many different procedures available in the treatment of shoulder instability, the Trillat procedure remains indicated in case of recurrent shoulder instability in elderly patient with an irreparable cuff tear or in case of hyperlaxity. Despite the constantly increasing number of arthroscopic assisted techniques, the open procedure remains a simple, reliable and fast surgical procedure with a shorter learning curve than the arthroscopic techniques. It consists in a partial osteotomy of the anterior cortical of the coracoid process which is then tilted and fixed with a screw into the anterior part of the scapula downwards and medially to obtain a re-centering effect due to the conjoint tendon on the humeral head when rotational movement are applied. This article aims to present a stepwise approach for the open surgical technique.

The prognosis of sickle cell disease (SCD) has greatly improved in recent years, resulting in an increased number of patients reporting musculoskeletal complications such as osteonecrosis of the femoral head. Total hip arthroplasty (THA) can be utilized to alleviate the pain associated with this disease. Although it is well known that hip arthroplasty for avascular necrosis (AVN) in SCD may represent a challenge for the surgeon, complications are frequent, and no guidelines exist to prevent these complications. Because patients with SCD will frequently undergo THA, we thought it necessary to fulfil the need for guidance recommendations based on experience, evidence and agreement from the literature. For all these reasons this review proposes guidelines that provide clinicians with a document regarding management of patients with SCD in the period of time leading up to primary THA. The recommendations provide guidance that has been informed by the clinical expertise and experience of the authors and available literature. Although this is not a systematic review since some papers may have been published in languages other than English, our study population consisted of 5,868 patients, including 2,126 patients with SCD operated on for THA by the senior author in the same hospital during 40 years and 3,742 patients reported in the literature. Cite this article: EFORT Open Rev 2020;5:641-651. DOI: 10.1302/2058-5241.5.190073

The findings of this study suggest that computer navigation may be safely used in a basic procedure for injection of stem cells.

Introduction Extra-articular resection (EAR) of the hip joint is prone to significant complications and morbidity. Thus, this study evaluates the cumulative incidences and main reasons of reoperation following EAR of primary malignant bone tumors (PMBT) of the hip to determine whether the outcomes are different between EAR of the pelvis and that of the proximal femur. Patients and methods Thirty-three patients presented with a PMBT of the proximal femur or pelvis were included in this study. Among all PMBTs, 58% originated from the pelvis and 42% were from the proximal femur. Twenty patients had chondrosarcomas (61%), 10 had osteosarcomas (30%), and 3 had sarcomas of another histological subtype (9%). Results The mean follow-up was of 76 months (range: 24–220 months). The cumulative probabilities of revision for any reason were 52% (95% confidence interval [CI] 30–70%) 5 years after surgery. The 5-year cumulative probabilities of revision were 13% (95% CI 4–27%), 24% (95% CI 10–42%), and 34% (95% CI 14–56%) for mechanical, infectious, and tumoral reasons, respectively. The 5-year cumulative probabilities of revision for any reason were 78% (95% CI 37–94%) and 14% (95% CI 2–38%) for the pelvis and proximal femur, respectively (p = 0.004). Posterior column preservation was significantly associated with more mechanical complications even after adjusting for the resection site (p = 0.043). Conclusion Half of patients undergoing EAR of the hip joint for PMBT of the proximal femur or acetabulum will require another operation. EAR of the pelvis is associated with significantly worse outcome than EAR of the proximal femur.

Purpose: Osteonecrosis is a rare event during or after pregnancy. Due to the low number of cases, there is no report of long-term results after conservative surgery in this population.Method: From 1992 to 2010, 145 consecutive female patients with unilateral symptomatic (94 stage I and 51 stage II) left hip osteonecrosis (ON) related to pregnancy were treated between 4 and 16 months after delivery with percutaneous mesenchymal stem cell (MSC) injection obtained from bone marrow concentration. The average total number of MSCs (counted as number of colonies forming units-fibroblast) injected in the hip was 185 000 ± 65 000 cells (range 95 000–240 000 cells).Results: At the most recent follow-up (average 15 years after hip surgery, range 8–25 years), among the 145 hips included in the study, 4 hips (2.7%) had collapsed and were treated with total hip arthroplasty (THA). Thirty-two of the 94 stage I had progressed to stage II; and 4 of the 51 stage II had progressed to stage III and collapse. The other 141 hips (97.3%) were without collapse and pain free. On MRI, as percentage of the volume of the femoral head, the osteonecrosis had decreased from 34.5% pre-operatively to 6% at the most recent follow-up. For women who had other children after treatment, a subsequent pregnancy was not associated with osteonecrosis.Conclusion: Patients with hip osteonecrosis following pregnancy had a low conversion rate to THA when treated early with cell therapy.

In summary, when the contralateral hip of the same patient is the control, after 40 years of follow-up, post-operative fractures occur 30 times more often on the side with PE cup than on the side with ceramic/ceramic bearing.