Biomechanical Comparison of Capsular Repair, Capsular Shift, and Capsular Plication for Hip Capsular Closure: Is a Single Repair Technique Best for All?

Background: In hip arthroscopy, the best capsular closure technique to prevent microinstability in some patients while preventing overconstraints in other patients has yet to be determined. Purpose: To evaluate the biomechanical effects of capsular repair, capsular shift, and combination capsular shift and capsular plication for closure of the hip capsule. Study Design: Controlled laboratory study. Methods: Eight cadaveric hips (4 male and 4 female hips; mean age, 55.7 years) were evaluated in 7 conditions: intact, vented, capsulotomy, side-to-side repair, side-to-side repair with capsular plication (interval closure between iliofemoral and ischiofemoral ligaments), capsular shift repair, and capsular shift repair with plication. Measurements, via a 360° goniometer, included internal and external rotation with 1.5 N·m of torque at 5° of extension and 0°, 30°, 60°, and 90° of flexion. In addition, the degree of maximum extension with 5 N·m of torque and the amount of femoral distraction with 40 N and 80 N of force were obtained. Repeated-measures analysis of variance and Tukey post hoc analyses were used to analyze differences between capsular conditions. Results: At lower hip positions (5° of extension, 0° and 30° of flexion), there was a significant increase in external rotation and total rotation after capsulotomy versus the intact state ( P < .05). At all hip flexion angles, there was a significant increase in external rotation, internal rotation, and total rotation as well as a significant increase in maximum extension after capsulotomy versus capsular shift with plication ( P < .05 for all). At all flexion angles, both capsular closure with side-to-side repair (with or without plication) and capsular shift without capsular plication were able to restore rotation, with no significant differences compared with the intact capsule ( P > .05). Among repair constructs, there were significant differences in range of motion between side-to-side repair and combined capsular shift with plication ( P < .05). Conclusion: At all positions, significantly increased rotational motion was seen after capsulotomy. Capsular closure was able to restore rotation similar to an intact capsule. Combined capsular shift and plication may provide more restrained rotation for conditions of hip microinstability but may overconstrain hips without laxity. Clinical Relevance: More advanced closure techniques or a combination of techniques may be needed for patients with hip laxity and microinstability. At the same time, simple repair may suffice for patients without these conditions.

Analysis of CircRNA Expression Profile of Pathological Bone Formation in Ankylosing Spondylitis

Objective: To screen and analyze the function of specific circular RNA involved of pathological bone formation in ankylosing spondylitis. Methods: From September 2019 to October 2020, Ossification capsule of 3 patients with ankylosing spondylitis developed hip joint fusion and capsule of 3 patients with femoral neck fracture were enrolled as the experimental group and the control group, respectively. The circular RNA expressions of hip capsule were analyzed by arraystar circRNA chip, bioinformatics analyses including the circRNA/miRNA/mRNA interaction network, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis.Results: The results showed that there totally were 25 up-regulated and 39 down-regulated differential circRNAs, among these circRNAs,we screened most up-regulated 10 circRNAs and most down-regulated 13 circRNAs in ankylosing spondylitis (FC≥2,P＜0.05). Further analysis demonstrated that two signal ways were most involved and correslated with the different circRNAs-“Focal Adhesion signal pathway” and “Rap1 signal pathway” Conclusion: The circular RNAs involved of pathological bone formation in ankylosing spondylitis were significantly different from that of the control group. These differentially expressed circular RNAs may be closely related to the occurrence and development of pathological bone formation in ankylosing spondylitis. Key words: CircRNA, Ankylosing spondylitis, Gene chip, Pathological bone formation

A systematic review and meta-analysis of the hip capsule innervation and its clinical implications

Detailed understanding of the innervation of the hip capsule (HC) helps inform surgeons’ and anaesthetists’ clinical practice. Post-interventional pain following radiofrequency nerve ablation (RFA) and dislocation following total hip arthroplasty (THA) remain poorly understood, highlighting the need for more knowledge on the topic. This systematic review and meta-analysis focuses on gross anatomical studies investigating HC innervation. The main outcomes were defined as the prevalence, course, density and distribution of the nerves innervating the HC and changes according to demographic variables. HC innervation is highly variable; its primary nerve supply seems to be from the nerve to quadratus femoris and obturator nerve. Many articular branches originated from muscular branches of the lumbosacral plexus. It remains unclear whether demographic or anthropometric variables may help predict potential differences in HC innervation. Consequently, primary targets for RFA should be the anterior inferomedial aspect of the HC. For THA performed on non-risk patients, the posterior approach with capsular repair appears to be most appropriate with the lowest risk of articular nerve damage. Care should also be taken to avoid damaging vessels and muscles of the hip joint. Further investigation is required to form a coherent map of HC innervation, utilizing combined gross and histological investigation.

Innervation of the Posterior Hip Capsule: A Cadaveric Study

Objective Recent studies of hip anatomy have turned to the posterior hip capsule to better understand the anatomic location of the posterior capsular sensory branches and identify nerves with potential for neural blockade. Current literature has shown the posterior hip capsule is primarily supplied by branches from the sciatic nerve, nerve to quadratus femoris, and superior gluteal nerve (1, 2). This cadaveric study investigated the gross anatomy of the posterior hip, while also identifying potential targets for hip analgesia, with emphasis on the superior gluteal nerve and nerve to quadratus femoris. Design Cadaveric study. Setting University of Texas Health San Antonio Anatomy Lab Methods 10 total cadavers (18 hips total), were posteriorly dissected identifying nerve to quadratus femoris, superior gluteal nerve, and sciatic nerve. Nerves were labeled with radio-opaque markers. Following the dissections, fluoroscopic images were obtained as sequential angles to identify neural anatomy and help expand anatomic knowledge for interventional pain procedures. Results The posterior hip capsule was supplied by the sciatic nerve in 1/16 hips, the nerve to quadratus femoris in 15/18 hips, and the superior gluteal nerve in 6/18 hips. Conclusions The nerve to quadratus femoris reliably innervates the posterior hip joint. Both the sciatic nerve and superior gluteal nerve may have small articular branches that may be involved in posterior hip innervation, but not this is not seen commonly. The results of this study may elucidate novel therapeutic targets for treatment of chronic refractory hip pain (i.e., the nerve to quadratus femoris).

SENSORY INNERVATION OF THE HIP JOINT AND REFERRED PAIN. A Systematic Review of the literature

Objectives The aim of this literature review was to establish consensus with respect to the anatomic features of the articular branches innervating the hip joint, and the distribution of sensory receptors within its capsule. Methods Five electronic databases were queried, between January 1945 and June 2019. Twenty-one original articles providing a detailed description of sensory receptors about the hip joint capsule (13) and its articular branches (8) were reviewed. Results The superior portions of the anterior capsule and the labrum were found to be the area of densest nociceptive innervation. Similar to the distribution of nociceptors, mechanoreceptor density was found to be higher anteriorly than posteriorly. Hip joint capsular innervation was found to consistently involve the femoral and obturator nerves, which supply the anterior capsule, and the nerve to the quadratus femoris which supplies the posterior capsule. The femoral and obturator and superior gluteal nerves supply articular branches to the most nociceptor-rich region of the hip capsule. Conclusions The femoral, obturator, and nerve to the quadratus femoris were found to consistently supply articular branches to both the anterior and posterior capsule of the hip joint. The anterior capsule, primarily supplied by the femoral and obturator nerves, and superior labrum appear to be the primary pain generators of the hip joint given their higher density of nociceptors and mechanoreceptors