The unstable hip in children with cerebral palsy: does an acetabuloplasty add midterm stability?

Purpose This study addresses whether an additional pelvic procedure is superior to a varus derotation osteotomy femur (VDRO) alone in unstable hips in children with cerebral palsy (CP). Methods All patients had unstable hips utilising the Melbourne Cerebral Palsy Hip Classification System (MCPHCS). We compared one group that underwent VDRO alone with one that had a combination of VDRO and Dega osteotomy (VDRO+). Measurements were taken before surgery, postoperatively, two years after surgery and at latest follow-up. Generalised estimating equations were used to account for known and unknown correlations between hips from bilateral cases. Results In total, 74 hips in 57 children fulfilled the inclusion criteria. There was no outcome difference between Gross Motor Function Classification System levels III, IV and V. Age at time of operation ranged from three to 16 years (mean 9.8 years). Mean follow-up was 49.1 months. In the VDRO group (28 hips) migration percentage (MP) changed from 61% preoperative to a final value of 35.7%. In the VDRO+ group (46 hips) the MP changed from 64.4% to 19.3%. At final follow-up 15 hips (54%) were stable in the VDRO group, 37 hips (83%) in the VDRO+ group. The odds ratio (OR) of hip stability at final follow-up was 3.5-times higher in the VDRO+ group versus the VDRO group (OR = 3.9; 95% confidence interval = 1.5 to 9.7; p = 0.004). Conclusion Reconstruction of unstable hips via VDRO + Dega in children with CP provides a higher likelihood of long-term stability than an isolated VDRO. Level of Evidence Level III, retrospective comparative study

The variation in hip stability measurements between supine and standing radiographs of dysplastic hips

Aims The aims of this study were to compare clinically relevant measurements of hip dysplasia on radiographs taken in the supine and standing position, and to compare Hip2Norm software and Picture Archiving and Communication System (PACS)-derived digital radiological measurements. Methods Preoperative supine and standing radiographs of 36 consecutive patients (43 hips) who underwent periacetabular osteotomy surgery were retrospectively analyzed from a single-centre, two-surgeon cohort. Anterior coverage (AC), posterior coverage (PC), lateral centre-edge angle (LCEA), acetabular inclination (AI), sharp angle (SA), pelvic tilt (PT), retroversion index (RI), femoroepiphyseal acetabular roof (FEAR) index, femoroepiphyseal horizontal angle (FEHA), leg length discrepancy (LLD), and pelvic obliquity (PO) were analyzed using both Hip2Norm software and PACS-derived measurements where applicable. Results Analysis of supine and standing radiographs resulted in significant variation for measurements of PT (p < 0.001) and AC (p = 0.005). The variation in PT correlated with the variation in AC in a limited number of patients (R2 = 0.378; p = 0.012). Conclusion The significant variation in PT and AC between supine and standing radiographs suggests that it may benefit surgeons to have both radiographs when planning surgical correction of hip dysplasia. We also recommend using PACS-derived measurements of AI and SA due to the poor interobserver error on Hip2Norm. Cite this article: Bone Joint J 2021;103-B(11):1662–1668.

Hip Stability Parameters with Dual Mobility, Modular Dual Mobility and Fixed Bearing in Total Hip Arthroplasty: an Analytical Evaluation

Background. Use of dual mobility in total hip arthroplasty has gained popularity due to the ability to reduce dislocation through increased jumping distance and impingement-free arc of movement. Recently, modular dual mobility systems were introduced to give the possibility to use dual mobility with standard metal-backed shells, however few has been studied to date regarding how jumping distance and the center of rotation changed with modular dual mobility. The objective of this study was to evaluate, through analytical simulation, how jumping distance and center of rotation change between dual mobility and standard cup with modular dual mobility or fixed bearings. Methods. 3D-models of dual mobility and standard press-fit cups with modular dual mobility or fixed bearings liners were used to simulate dual mobility, modular dual mobility and fixed bearings implant configurations, matched for same cup size, according to same cup position, different femoral head diameters. Jumping distance was calculated and center of rotation lateralization was measured for different sizes.Results. Jumping distance with modular dual mobility was reduced by -3.9mm to -8.6mm in comparison with dual mobility, from 48 to 64mm sizes. Jumping distance with modular dual mobility resulted comparable to jumping distance with polyethylene fixed bearings with Ø36mm femoral head but increased by +1.1mm and +1.4mm than jumping distance with ceramic fixed bearings with Ø36 and Ø40mm femoral heads for sizes >54mm. Modular dual mobility lateralized the center of rotation up to +2.5mm and +4.0mm in comparison with dual mobility and fixed bearings, respectively. Conclusions. Jumping distance with modular dual mobility resulted lower than dual mobility and comparable to fixed bearings polyethylene liner with Ø36mm femoral head for larger sizes. Modular dual mobility lateralized the center of rotation in comparison with both dual mobility and fixed bearings cups.Trial Registration. Not applicable.

Hip Stability Parameters with Dual Mobility, Modular Dual Mobility and Fixed Bearing in Total Hip Arthroplasty: an Analytical Evaluation.

Background. Use of dual mobility in total hip arthroplasty has gained popularity due to the ability to reduce dislocation through increased jumping distance and impingement-free arc of movement. Recently, modular dual mobility systems were introduced to give the possibility to use dual mobility with standard metal-backed shells, however few has been studied to date regarding how jumping distance and the center of rotation changed with modular dual mobility. The objective of this study was to evaluate, through analythical simulation, how jumping distance and center of rotation change between dual mobility and standard cup with modular dual mobility or fixed bearings. Methods. 3D-models of dual mobility and standard press-fit cups with modular dual mobility or fixed bearings liners were used to simulate dual mobility, modular dual mobility and fixed bearings implant configurations, matched for same cup size, according to same cup position, different femoral head diameters. Jumping distance was calculated and center of rotation lateralization was measured for different sizes.Results. Jumping distance with modular dual mobility was reduced by -3.9mm to -8.6mm in comparison with dual mobility, from 48 to 64mm sizes. Jumping distance with modular dual mobility resulted comparable to jumping distance with polyethylene fixed bearings with Ø36mm femoral head but increased by +1.1mm and +1.4mm than jumping distance with ceramic fixed bearings with Ø36 and Ø40mm femoral heads for sizes >54mm. Modular dual mobility lateralized the center of rotation up to +2.5mm and +4.0mm in comparison with dual mobility and fixed bearings, respectively. Conclusions. Jumping distance with modular dual mobility resulted lower than dual mobility and comparable to fixed bearings polyethylene liner with Ø36mm femoral head for larger sizes. Modular dual mobility lateralized the center of rotation in comparison with both dual mobility and fixed bearings cups.

The role of the iliofemoral ligament as a stabilizer of the hip joint

The purpose of this systematic literature review is to analyse the role of the iliofemoral ligament (ILFL) as a hip joint stabilizer in the current literature. A total of 26 articles were included in the review. The ILFL is the largest hip ligament consisting of two distinct arms and is highly variable, both in its location and overall size, and plays a primary role in hip stability; in the case of hip dislocation, the iliofemoral ligament tear does not heal, resulting in a persistent anterior capsule defect. Clinically, the ILFL is felt to limit external rotation in flexion and both internal and external rotation in extension. The abduction–hyperextension–external rotation (AB-HEER) test is overall the most accurate test to detect ILFL lesions. Injuries of the ILFL could be iatrogenic or a consequence of traumatic hip instability, and can be accurately studied with magnetic resonance imaging. Different arthroscopic and open techniques have been described in order to preserve the ILFL during surgery and, in case of lesions, several procedures with good to excellent results have been reported in the existing literature. The current systematic review, focusing only on the ILFL of the hip, summarizes the existing knowledge on anatomy, imaging and function and contributes to the further understanding of the ILFL, confirming its key role in anterior hip stability. Future studies will have to develop clinical tests to evaluate the functionality and stability of the ILFL. Cite this article: EFORT Open Rev 2021;6:545-555. DOI: 10.1302/2058-5241.6.200112

Dual Modular Titanium Alloy Femoral Stem Failure Mechanisms and Suggested Clinical Approaches

Titanium (Ti) alloys have been proven to be one of the most suitable materials for orthopaedic implants. Dual modular stems have been introduced to primary total hip arthroplasty (THA) to enable better control of the femoral offset, leg length, and hip stability. This systematic review highlights information acquired for dual modular Ti stem complications published in the last 12 years and offers a conclusive discussion of the gathered knowledge. Articles referring to dual modular stem usage, survivorship, and complications in English were searched from 2009 to the present day. A qualitative synthesis of literature was carried out, excluding articles referring solely to other types of junctions or problems with cobalt-chromium alloys in detail. In total, 515 records were identified through database searching and 78 journal articles or conference proceedings were found. The reasons for a modular neck fracture of a Ti alloy are multifactorial. Even though dual modular stems have not shown any clinical benefits for patients and have been associated with worse results regarding durability than monolithic stems, some designs are still marketed worldwide. Orthopaedic surgeons should use Ti6Al4V dual modular stem designs for primary THA in special cases only.

Inclination, hip abduction, orientation, and tone affect weight-bearing in standing devices

PURPOSE: With children who are unable to stand or walk independently in the community, therapists commonly use standing devices to assist lower-extremity weight-bearing which is important for bone and muscle health. In addition, positioning in hip abduction may improve hip stability and range of motion. This is the first study to explore the effect of angle of inclination, hip abduction, body orientation, and tone on weight-bearing in pediatric standing devices. METHODS: This descriptive exploratory study used a convenience sample of 15 participants (2 with normal tone, 5 with generalized hypotonia, and 8 with hypertonia) (mean age of 5 years and 10 months, range of 3 years 4 months to 9 years 7 months); 13 of whom used standing devices at home, as well as 2 typically developing siblings (normal tone). Each child stood in 36 positions to measure the amount of weight-bearing through footplates. RESULTS: Weight-bearing was highest with 60 degrees of abduction and no inclination (upright) in supine positioning for children with low and normal tone. Children with high muscle tone bore most weight through their feet with no abduction (feet together) and no inclination (upright) in prone positioning. Overall, supine positioning resulted in more weight-bearing in all positions for children with low and normal tone. Prone positioning resulted in slightly more weight-bearing in all positions for children with high tone. CONCLUSIONS: Weight-bearing was affected by all three of the variables (inclination, abduction, and orientation) for participants with high, normal, and low tone. To determine optimal positioning, all standers should include a system to measure where and how much weight-bearing is occurring in the device.