Traumatic native hip dislocation in the absence of acetabular or femoral fracture in adults: a retrospective study reporting clinical and radiological outcomes from a major trauma centre in the United Kingdom.

INTRODUCTION: Posterior native hip dislocations (NHD) are high-energy injuries. Thompson-Epstein Type I dislocations describe those without significant associated femoral or acetabular fracture. The aim of this study was to compare the clinical and radiological outcomes of patients with Type I NHDs. We also evaluate the association between radiological indicators of femoroacetabular impingement (FAI) and NHD. PATIENTS AND METHODS: A retrospective study from January 2012 to May 2021 compared skeletally mature patients (⩾16 years) with Type I posterior NHD to age and gender-matched controls with Type II-V posterior NHD. Patient demographics, mechanism of injury, complications and patient-reported outcome measures (PROMs) are presented. Post reduction radiographs and computed tomography were used to assess for FAI. Univariate analyses were performed to evaluate radiological outcomes. RESULTS: 13 patients (77% male) with Type I posterior NHD were compared to a control group of 40 patients (80% male) with Type II-V posterior NHD. 11 patients in the study group and 14 in the control group experienced isolated injuries (p = 0.01). Post-reduction complications were similar. The study group had significantly lower post-injury osteoarthritis incidence (n = 0) compared to controls (n = 18, p = 0.0083). Patients reported a mean Oxford Hip Score of 43.5 ± 2.2 and EQ-5D-VAS score of 87.1 ± 7.4, with 6 patients indicating minimal symptoms across all EQ-5D-5L domains. Radiological femoroacetabular impingement (FAI) was prevalent in both groups, especially among males. CONCLUSIONS: Patients who underwent emergent closed reduction of Type I NHD demonstrated good short to medium term outcomes. Our radiological findings suggest a high prevalence of FAI. Future work should aim to quantify longer term outcomes following this injury. We call for further comparative studies of patients who suffer NHD with and without fractures to aid our understanding of risk factors. Given the rarity of this injury, multicentre efforts will be required to capture large numbers of patients.

Plate-Assisted Intramedullary Nailing of Gustilo Type IIIB Open Tibial Diaphyseal Fractures: Does Adjunctive Plate Retention Affect Complication Rate?

OBJECTIVES: To investigate the complication rates after use of retained adjunctive plate (RAP) fixation with intramedullary nailing of Gustilo-Anderson type IIIB open tibia fractures, as part of a 2-stage orthoplastic approach. DESIGN: Consecutive cohort study. PATIENTS/PARTICIPANTS: One hundred and thirty-seven consecutive patients with a Gustilo-Anderson type IIIB open diaphyseal tibia fracture (OTA/AO 42) treated between May 2014 and January 2018. Ninety-eight patients (RAP = 67; non-RAP = 31) met the inclusion criteria and underwent 2-stage reconstruction. All patients were treated using a small fragment adjunctive plate to hold the fracture reduced before intramedullary nailing. INTERVENTION: At stage 2, the temporary small fragment (in-fix) plate was removed and the site further thoroughly debrided. After this, the fracture is reduced and held with a new small fragment plate to facilitate the definitive intramedullary nailing. This new plate was either retained (RAP) as part of the definitive fixation at second stage or removed before wound coverage. MAIN OUTCOME MEASUREMENT: The main outcome measures were reoperation rate, deep infection, nonunion, and flap-related complication. RESULTS: Six patients (6/98, 6.1%) proceeded to nonunion (RAP 5/67, non-RAP 1/31). This was not significant (P = 0.416). Two hundred twelve operations were undertaken, and the median was 2. Sixteen (16/212, 7.5%) complication-related reoperations were undertaken, affecting 8 patients (8/67, 11.9%) in the RAP group. Eight patients (8/98, 8.2%) developed a deep infection (RAP 6/67, non-RAP 2/31). This was not significant (P = 0.674). CONCLUSIONS: In the context of an orthoplastic approach, the use of a RAP with definitive intramedullary nailing does not seem to significantly increase the rate of deep infection or nonunion in patients with type IIIB open tibial shaft fractures. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Two-Stage Combined Ortho-Plastic Management of Type IIIB Open Diaphyseal Tibial Fractures Requiring Flap Coverage: Is the Timing of Debridement and Coverage Associated With Outcomes?

OBJECTIVE: To delineate whether timing to initial debridement and definitive treatment had an effect on patient outcomes in those undergoing 2-stage ortho-plastic management of Gustilo-Anderson type IIIB open tibial diaphyseal fractures. DESIGN: Retrospective comparative cohort study over a 2-year period. SETTING: Level 1 trauma center. PATIENTS/PARTICIPANTS: A total of 148 patients were identified. After exclusion of ankle fractures, nondiaphyseal fractures and those who did not undergo 2-stage ortho-plastic management, 45 patients were eligible for final analysis. INTERVENTION: Time to initial debridement and definitive management. MAIN OUTCOME MEASUREMENT: Deep infection. Secondary outcomes being nonunion and flap failure. Multiple linear regression was used for outcomes. We assumed a priori that P values of less than 0.05 were significant. RESULTS: Mean age was 54 years (SD 23.0), with 28 men and 17 women. Over a mean 2-year follow-up, there were 4 (4/45) deep infections, 2 infection-associated flap failures, and 1 vascular flap failure. All patients progressed to union. The mean time to initial debridement for the whole cohort was 19 hours (SD 12.3), and the mean time to definitive reconstruction was 65 hours (SD 51.7). Longer time to both initial debridement and definitive reconstruction was not found to be significantly associated with deep infection, infected flap failure, or nonunion. CONCLUSIONS: Using a 2-stage ortho-plastic operative algorithm, timing to initial debridement and definitive fixation with soft-tissue coverage was not associated with negative outcomes. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Temperature-induced switching of enzyme activity with smart polymer-enzyme conjugates.

A method for thermally induced switching of enzyme activity has been developed, based on the site-directed conjugation of end-reactive temperature-responsive polymers to a unique cysteine (Cys) residue positioned near the enzyme active site. The reversible temperature-induced collapse of N,N-dimethylacrylamide (DMA)/N-4-phenylazo-phenylacrylamide (AZAAm) copolymers (DMAAm) has been used as a molecular switch to control the catalytic activity of endoglucanase 12A (EG 12A). The polymer was conjugated to the EG 12A site-directed mutant N55C, directly adjacent to the cellulose binding cleft, and to the S25C mutant, where the conjugation site is more distant. The N55C conjugate displayed a larger activity shutoff efficiency in the collapsed polymer state than the S25C conjugate. Increasing the polymer molecular weight was also shown to increase the shutoff efficiency of the switch. Related to these effects of conjugation site and polymer size, the switching efficiency was found to be strongly dependent on substrate size. With a small substrate, o-nitrophenyl-beta-d-cellobioside (ONPC), there was minimal blocking of enzyme activity when the polymer was in the expanded state. With a large substrate, hydroxyethyl cellulose (HEC), there was a large reduction of enzyme activity in the polymer expanded state, even with relatively small polymer chains, and a further reduction when the polymer was collapsed. Similar general trends for the interactive effects of conjugation site, polymer size, and substrate size were observed for immobilized conjugates. Kinetic studies demonstrated that the switching activity was due to the blocking of substrate association by the collapsed polymers. These investigations provide mechanistic insight that can be utilized to design molecular switches for a variety of stimuli-responsive polymer-protein conjugates.

Photoresponsive polymer-enzyme switches.

The ability to photoregulate enzyme activities could provide important new opportunities for development of diagnostic assays, sequential bioprocessing, and lab assays in both traditional and microfluidic formats. We show here that the photoinduced changes in the size and hydration of a "smart" polymer chain coil can be used to regulate substrate access and enzyme activity when conjugated to the enzyme at a specific point just outside the active site. The photoresponsive polymers thus serve jointly as antennae and actuators that reversibly respond to distinct optical signals to switch the polymer-enzyme conjugates on and off, and work when the conjugate is free in solution or when immobilized on magnetic beads.