Relationship Between Hip Capsular Thickness and Instability After Previous Hip Arthroscopic Surgery: A Matched-Cohort Analysis.

Background: Thinner anterior hip capsules are associated with hip laxity, but there is little known about the impact of capsular thickness on the development of instability after primary hip arthroscopic surgery. Purpose: To investigate the relationship between hip capsular thickness as measured on preoperative magnetic resonance imaging (MRI) and the development of hip instability after hip arthroscopic surgery for femoroacetabular impingement. Study Design: Case-control study; Level of evidence, 3. Methods: We reviewed revision hip arthroscopic procedures performed between January 1, 2019, and May 1, 2021, at a single institution. Inclusion criteria were preoperative MRI/magnetic resonance arthrography, completion of the study traction protocol, and asymmetric distraction between the hips of ≥3 mm on examination under anesthesia. A comparison group of patients treated for femoroacetabular impingement with primary hip arthroscopic surgery who did not develop capsular instability were matched 1:1 to the patients with instability. Superolateral hip capsular thickness was measured on MRI before index surgery. Analysis was conducted using independent-samples t tests and multivariable linear regression. Results: A total of 44 patients were included, with 22 patients each in the instability and no-instability groups. The mean capsular thickness was lower in the patients with hip instability than in those without (1.9 ± 0.6 vs 3.4 ± 1.1 mm, respectively; P < .001). Decreased capsular thickness was significantly associated with hips with instability versus no-instability (ß = -1.468 [95% CI, -2.049 to -0.887]; P < .001). Conclusion: Thinner preoperative hip capsules in the region of the iliofemoral ligament were seen in patients who subsequently underwent revision arthroscopic surgery for hip instability compared to patients who underwent primary hip arthroscopic surgery without subsequent revision. Patients at a higher risk for the development of postoperative hip instability had a superolateral hip capsular thickness of <2 mm.

Fixation Techniques for Scaphoid Nonunion.

Scaphoid fractures are common injuries with high risk of nonunion. Various fixation techniques exist for managing scaphoid nonunions, including Kirschner wires, single or dual headless compression screws, combination fixation techniques, volar plating, and compressive staple fixation. The indication for each fixation technique varies depending on the patient, type of nonunion, and clinical scenario.

Meshed Acellular Dermal Matrix for Two-Staged Prepectoral Breast Reconstruction: An Institutional Experience.

The introduction of acellular dermal matrix (ADM) to breast reconstruction has allowed surgeons to reexplore the prepectoral implant placement technique in postmastectomy breast reconstruction. Our institution adopted a novel approach using meshed ADM to lessen the financial burden of increased ADM utilization with the prepectoral breast reconstruction. This is a retrospective, single-center review of two-stage prepectoral breast reconstruction using meshed human-derived ADM for anterior prosthesis coverage. Patient demographics, oncologic data, perioperative characteristics, and complications were examined and reported as means with standard deviations. Cost-saving with the meshed technique was evaluated. Forty-eight patients (72 breasts) with a mean age of 48.5 ± 15.0 years (range 26-70 years) were included in the study. The mean follow-up time was 13.2 ± 4.4 months (range 4.1-25.8 months). Nineteen breasts (24.6%) experienced complications, with seromas being the most common complication (12.5%, n = 9). Expander removal and reoperation occurred at a rate of 8.3 and 9.7%, respectively. The average time to drain removal was 18.8 ± 6.6 days (range 8-32 days). Meshed ADM provided an average cost savings of $6,601 for unilateral and $13,202 for bilateral reconstructions. Our study found that human-derived meshed ADM can be safely used in two-staged prepectoral tissue expander-based breast reconstruction and can result in significant cost savings.

Previous Arthroscopic Hip Surgery Increases Axial Distractibility Compared to the Native Contralateral Hip and May Suggest Instability.

PURPOSE: To compare intraoperative hip joint distractibility between hips that previously underwent arthroscopic surgery and the contralateral hip with no history of surgical manipulation. METHODS: Patients undergoing revision hip arthroscopy between April 2019 and December 2020, who previously underwent arthroscopic hip surgery for femoroacetabular impingement syndrome, were prospectively enrolled. Exclusion criteria were any contralateral hip surgery. Before instrumentation, fluoroscopic images of both hips were obtained at 25 lbs traction intervals up to 100 lbs. Total joint space was measured at each traction interval. Distraction was calculated as the difference between the baseline joint space and the total joint space at each subsequent traction interval. Wilcoxon signed ranks tests and McNemar tests were used to compare distraction between revision and native contralateral hips. RESULTS: Forty-seven patients were included. Mean distraction of operative hips was significantly greater than mean distraction of nonoperative hips at traction intervals of 50 lbs (2.13 vs 1.04 mm, P = .002), 75 lbs (6.39 vs 3.70 mm, P < .001), and 100 lbs (8.24 vs 5.39, P < .001). Mean total joint space of operative hips was significantly greater than mean total joint space of nonoperative hips at traction intervals of 50 lbs (6.60 vs 5.39 mm, P < .001), 75 lbs (10.86 vs 8.05 mm, P < .001), and 100 lbs (12.73 vs 9.73, P < .001). A greater percentage of operative hips achieved all distraction thresholds, in 2-mm intervals up to 10-mm, at each traction interval. CONCLUSIONS: In the majority of patients undergoing revision hip arthroscopy, previous arthroscopic hip surgery increases axial distractibility of the hip joint compared with the native contralateral hip at axial traction forces of 50-100 lbs. Increased axial distractibility following hip arthroscopy may be suggestive of hip instability and can be assessed on a stress examination with the patient under anesthesia. LEVEL OF EVIDENCE: III, case-control study.

Capsular Repair During Hip Arthroscopy Demonstrates Restoration of Axial Distraction Resistance in an in Vivo Intraoperative Testing Model.

BACKGROUND: Cadaveric models demonstrate that failure of hip capsular repair is dependent on the robustness of the repair construct. In vivo data on capsular repair construct efficacy are limited. We investigated the effect of a figure-of-8 capsular repair on hip distraction resistance relative to native and post-capsulotomy states. We hypothesized that an unrepaired capsulotomy would demonstrate increased axial distraction compared with the native state and that capsular repair would restore distraction resistance to native levels. METHODS: Patients undergoing primary hip arthroscopy by a single surgeon were prospectively enrolled between March 2020 and June 2020. Prior to any instrumentation, fluoroscopic images of the operative hip were obtained at 12.5-lbs (5.7-kg) traction intervals, up to 100 lbs (45.4 kg). Anterolateral, modified anterior, and distal anterolateral portals were established. Following interportal capsulotomy, labral repair, and osteochondroplasty, fluoroscopic images were reobtained at each traction interval. Capsular repair was performed with use of a figure-of-8 suture configuration. Traction was reapplied and fluoroscopic images were again obtained. Joint distraction distance was measured at each traction interval for all 3 capsular states. Anteroposterior pelvic radiographs were utilized to scale fluoroscopic images to obtain joint space measurements in millimeters. RESULTS: A total of 31 hips in 31 patients were included. Capsulotomy resulted in significant increases in distraction distance from 25 (11.3 kg) to 100 lbs of traction compared with both native and capsular repair states (all comparisons, p ≤ 0.017). Capsular repair yielded a significantly greater distraction distance compared with the native state at 37.5 lbs (17.0 kg; 5.49 versus 4.98 mm, respectively; p = 0.012) and 50 lbs (22.7 kg; 6.08 versus 5.35 mm; p < 0.001). The mean difference in distraction distance between native and capsular repair states from 25 to 100 lbs of traction was 0.01 mm. CONCLUSIONS: This in vivo model demonstrates that an unrepaired interportal capsulotomy significantly increases axial distraction distance compared with the native, intact hip capsule. Performing a complete capsular closure reconstitutes resistance to axial distraction intraoperatively. Future research should evaluate the in vivo effects and associated clinical outcomes of other published capsular repair techniques and assess the durability of capsular repairs over time.

Joint Venting Prior to Hip Distraction Minimizes Traction Forces During Hip Arthroscopy.

PURPOSE: This study evaluates the effect of venting on distraction of the hip during arthroscopy on a post-free traction table for fixed traction forces ranging from 0 to 100 pounds (lbs). METHODS: Patients underwent surgery by the senior author (S.K.A.) between November 2018 and July 2019. Inclusion criteria were primary hip arthroscopy requiring central compartment access. Patients were positioned in 10-15° Trendelenburg on a post-free traction table. Prior to instrumentation, fluoroscopic images of the operated hip joint were taken at 25-lb intervals from 0 to 100 lbs of axial traction. Traction was released for 15 minutes. Venting with 20 mL of air was performed and fluoroscopic images were repeated at all traction intervals. Joint displacement was measured at all intervals. An unvented control group underwent the same axial traction protocol for comparison. RESULTS: Sixty-one consecutive patients underwent study protocol. Fifty-eight hips in 57 patients were included. Thirty-two (55.2%) were female; mean age was 31 ± 13 years and mean body mass index was 25.7 ± 6.2. Paired samples analysis demonstrated mean differences in distraction distance prior to and after venting of 0.27, 2.60, 4.09, 4.54, and 2.31 mm at 0, 25, 50, 75, and 100 lbs of traction, which were significant (P < .001) at all traction intervals. Significantly more vented hips distracted at least 10 mm at 25-100 lbs traction (P ≤ .001). An unvented control group showed no significant differences between the first and second traction application. CONCLUSIONS: Venting prior to applying traction on a post-free traction table increases the distraction distance achieved for a given traction force at multiple levels of traction in comparison to the pre-vented state. Our results suggest venting the hip joint prior to the application of traction may serve to reduce the maximal amount of traction required to safely instrument the hip arthroscopically. LEVEL OF EVIDENCE: IV, case series.

Sorption of H2 to open metal sites in a metal-organic framework: a symmetry-adapted perturbation theory analysis.

Metal-organic frameworks (MOFs) show considerable promise as materials for gas storage and separation. Many MOF structures have open metal sites, which allow for coordination of gas molecules to the metal centers. In this work, we use coupled-cluster and symmetry-adapted perturbation theory to probe the interaction between hydrogen gas and unsaturated metal sites in mimic structures based on the MOF HKUST-1. The interactions are of a mixed electrostatic/dispersive nature, with the relative magnitudes of these components dependent on the metal center. The strongest binding was found for magnesium- and zinc-containing MOFs, with an overall interaction energy of -4.5 kcal mol(-1).