Modification of the structural stability of human serum albumin in rheumatoid arthritis.

Differential scanning calorimetry (DSC) can indicate changes in structure and/or concentration of the most abundant proteins in a biological sample via heat denaturation curves (HDCs). In blood serum for example, HDC changes result from either concentration changes or altered thermal stabilities for 7-10 proteins and has previously been shown capable of differentiating between sick and healthy human subjects. Here, we compare HDCs and proteomic profiles of 50 patients experiencing joint-inflammatory symptoms, 27 of which were clinically diagnosed with rheumatoid arthritis (RA). The HDC of all 50 subjects appeared significantly different from expected healthy curves, but comparison of additional differences between the RA and the non-RA subjects allowed more specific understanding of RA samples. We used mass spectrometry (MS) to investigate the reasons behind the additional HDC changes observed in RA patients. The HDC differences do not appear to be directly related to differences in the concentrations of abundant serum proteins. Rather, the differences can be attributed to modified thermal stability of some fraction of the human serum albumin (HSA) proteins in the sample. By quantifying differences in the frequency of artificially induced post translational modifications (PTMs), we found that HSA in RA subjects had a much lower surface accessibility, indicating potential ligand or protein binding partners in certain regions that could explain the shift in HSA melting temperature in the RA HDCs. Several low abundance proteins were found to have significant changes in concentration in RA subjects and could be involved in or related to binding of HSA. Certain amino acid sites clusters were found to be less accessible in RA subjects, suggesting changes in HSA structure that may be related to changes in protein-protein interactions. These results all support a change in behavior of HSA which may give insight into mechanisms of RA pathology.

Sloppy model analysis identifies bifurcation parameters without normal form analysis.

Bifurcation phenomena are common in multidimensional multiparameter dynamical systems. Normal form theory suggests that bifurcations are driven by relatively few combinations of parameters. Models of complex systems, however, rarely appear in normal form, and bifurcations are controlled by nonlinear combinations of the bare parameters of differential equations. Discovering reparameterizations to transform complex equations into a normal form is often very difficult, and the reparameterization may not even exist in a closed form. Here we show that information geometry and sloppy model analysis using the Fisher information matrix can be used to identify the combination of parameters that control bifurcations. By considering observations on increasingly long timescales, we find those parameters that rapidly characterize the system's topological inhomogeneities, whether the system is in normal form or not. We anticipate that this novel analytical method, which we call time-widening information geometry (TWIG), will be useful in applied network analysis.

Utilizing Nonequilibrium Isotope Enrichments to Dramatically Increase Turnover Measurement Ranges in Single Biopsy Samples from Humans.

The synthesis of new proteins and the degradation of old proteins in vivo can be quantified in serial samples using metabolic isotope labeling to measure turnover. Because serial biopsies in humans are impractical, we set out to develop a method to calculate the turnover rates of proteins from single human biopsies. This method involved a new metabolic labeling approach and adjustments to the calculations used in previous work to calculate protein turnover. We demonstrate that using a nonequilibrium isotope enrichment strategy avoids the time dependent bias caused by variable lag in label delivery to different tissues observed in traditional metabolic labeling methods. Turnover rates are consistent for the same subject in biopsies from different labeling periods, and turnover rates calculated in this study are consistent with previously reported values. We also demonstrate that by measuring protein turnover we can determine where proteins are synthesized. In human subjects a significant difference in turnover rates differentiated proteins synthesized in the salivary glands versus those imported from the serum. We also provide a data analysis tool, DeuteRater-H, to calculate protein turnover using this nonequilibrium metabolic 2H2O method.

Suture Anchor Repair of a Combined Tear of the Proximal Iliotibial Band and Tensor Fascia Lata.

A combined tear of the proximal iliotibial band and tensor fascia lata is an uncommon injury, and currently, the body of literature on the topic is limited. The suture anchor repair technique described in this article allows anatomic restoration of the proximal iliotibial band and tensor fascia lata.

Assessment of Skeletal Maturity and Postoperative Growth Disturbance After Anterior Cruciate Ligament Reconstruction in Skeletally Immature Patients: A Systematic Review.

BACKGROUND: Growth disturbance is an uncommon but potentially serious complication after anterior cruciate ligament (ACL) reconstruction in skeletally immature patients. PURPOSE: To describe how the pediatric ACL literature has assessed preoperative skeletal maturity and the amount of growth remaining and to comprehensively review the incidence, reporting, and monitoring of postoperative growth disturbance. STUDY DESIGN: Systematic review; Level of evidence, 4. METHODS: This review included studies reporting original research of clinical outcomes of skeletally immature patients after ACL reconstruction. Patient characteristics, surgical techniques, preoperative assessments of skeletal maturity or growth remaining, and postoperative assessments of growth disturbances were extracted. RESULTS: A total of 100 studies met inclusion criteria. All studies reported chronological age, and 28 studies (28%) assessed skeletal age. A total of 44 studies (44%) used Tanner staging, and 12 studies (12%) obtained standing hip-to-ankle radiographs preoperatively. In total, 42 patients (2.1%) demonstrated a leg length discrepancy (LLD) >10 mm postoperatively, including 9 patients (0.5%) with LLD >20 mm; furthermore, 11 patients (0.6%) with LLD underwent growth modulation. Shortening was the most common deformity overall, but overgrowth was reported more frequently in patients who had undergone all-epiphyseal techniques. Most LLDs involved the femur (83%). A total of 26 patients (1.3%) demonstrated a postoperative angular deformity ≥5°, and 9 of these patients underwent growth modulation. The most common deformities were femoral valgus (41%), tibial recurvatum (33%), and tibial varus (22%). Although standing hip-to-ankle radiographs were the most common radiographic assessment of growth disturbance, most studies inadequately reported the clinical and radiographic methods of assessment for growth disturbance. Additionally, only 35% of studies explicitly followed patients to skeletal maturity. CONCLUSION: This systematic review described significant variability in the reporting and monitoring of growth-related complications after ACL reconstruction in skeletally immature patients. The incidence of LLD and angular deformity appeared to be low, but the quality of research was not comprehensive enough for accurate assessment. REGISTRATION: CRD42019136059 (PROSPERO).

Descriptive Epidemiology From the Research in Osteochondritis Dissecans of the Knee (ROCK) Prospective Cohort.

BACKGROUND: Osteochondritis dissecans (OCD) occurs most commonly in the knees of young individuals. This condition is known to cause pain and discomfort in the knee and can lead to disability and early knee osteoarthritis. The cause is not well understood, and treatment plans are not well delineated. The Research in Osteochondritis Dissecans of the Knee (ROCK) group established a multicenter, prospective cohort to better understand this disease. PURPOSE: To provide a baseline report of the ROCK multicenter prospective cohort and present a descriptive analysis of baseline data for patient characteristics, lesion characteristics, and clinical findings of the first 1000 cases enrolled into the prospective cohort. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Patients were recruited from centers throughout the United States. Baseline data were obtained for patient characteristics, sports participation, patient-reported measures of functional capabilities and limitations, physical examination, diagnostic imaging results, and initial treatment plan. Descriptive statistics were completed for all outcomes of interest. RESULTS: As of November 2020, a total of 27 orthopaedic surgeons from 17 institutions had enrolled 1004 knees with OCD, representing 903 patients (68.9% males; median age, 13.1 years; range, 6.3-25.4 years), into the prospective cohort. Lesions were located on the medial femoral condyle (66.2%), lateral femoral condyle (18.1%), trochlea (9.5%), patella (6.0%), and tibial plateau (0.2%). Most cases involved multisport athletes (68.1%), with the most common primary sport being basketball for males (27.3% of cases) and soccer for females (27.6% of cases). The median Pediatric International Knee Documentation Committee (Pedi-IKCD) score was 59.9 (IQR, 45.6-73.9), and the median Pediatric Functional Activity Brief Scale (Pedi-FABS) score was 21.0 (IQR, 5.0-28.0). Initial treatments were surgical intervention (55.4%) and activity restriction (44.0%). When surgery was performed, surgeons deemed the lesion to be stable at intraoperative assessment in 48.1% of cases. CONCLUSION: The multicenter ROCK group has been able to enroll the largest knee OCD cohort to date. This information is being used to further understand the pathology of OCD, including its cause, associated comorbidities, and initial presentation and symptoms. The cohort having been established is now being followed longitudinally to better define and elucidate the best treatment algorithms based on these presenting signs and symptoms.

Early Operative Versus Delayed Operative Versus Nonoperative Treatment of Pediatric and Adolescent Anterior Cruciate Ligament Injuries: A Systematic Review and Meta-analysis.

BACKGROUND: Treatment options for pediatric and adolescent anterior cruciate ligament (ACL) injuries include early operative, delayed operative, and nonoperative management. Currently, there is a lack of consensus regarding the optimal treatment for these injuries. PURPOSE/HYPOTHESIS: The purpose was to determine the optimal treatment strategy for ACL injuries in pediatric and adolescent patients. We hypothesized that (1) early ACL reconstruction results in fewer meniscal tears than delayed reconstruction but yields no difference in knee stability and (2) when compared with nonoperative management, any operative management results in fewer meniscal tears and cartilage injuries, greater knee stability, and higher return-to-sport rates. STUDY DESIGN: Systematic review and meta-analysis; Level of evidence, 4. METHODS: A systematic search of databases was performed including PubMed, Embase, and Cochrane Library using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Inclusion criteria were a pediatric and adolescent patient population (≤19 years old at surgery), the reporting of clinical outcomes after treatment of primary ACL injury, and original scientific research article. Exclusion criteria were revision ACL reconstruction, tibial spine avulsion fracture, case report or small case series (<5 patients), non-English language manuscripts, multiligamentous injuries, and nonclinical studies. RESULTS: A total of 30 studies containing 50 cohorts and representing 1176 patients met our criteria. With respect to nonoperative treatment, knee instability was observed in 20% to 100%, and return to preinjury level of sports ranged from 6% to 50% at final follow-up. Regarding operative treatment, meta-analysis results favored early ACL reconstruction over delayed reconstruction (>12 weeks) for the presence of any meniscal tear (odds ratio, 0.23; P = .006) and irreparable meniscal tear (odds ratio, 0.31; P = .001). Comparison of any side-to-side differences in KT-1000 arthrometer testing did not favor early or delayed ACL reconstruction in either continuous mean differences (P = .413) or proportion with difference ≥3 mm (P = .181). Return to preinjury level of competition rates for early and delayed ACL reconstruction ranged from 57% to 100%. CONCLUSION: Delaying ACL reconstruction in pediatric or adolescent patients for >12 weeks significantly increased the risk of meniscal injuries and irreparable meniscal tears; however, early and delayed operative treatment achieved satisfactory knee stability. Nonoperative management resulted in high rates of residual knee instability, increased risk of meniscal tears, and comparatively low rates of return to sports.

All-Suture Anatomic Footprint Repair of the Distal Triceps Tendon.

Distal triceps ruptures are an uncommon injury, and currently, there is a lack of consensus on the optimal surgical technique for repair. The traditional transosseous cruciate repair has been shown to be nonanatomic and to have a higher failure rate and be biomechanically inferior to suture anchor repairs. The use of anchors significantly increases procedure cost and theoretically increases the risk of complications related to drill and anchor placement. The technique described in this article allows anatomic restoration of the triceps tendon while avoiding the increased cost and risk that may be associated with suture anchor placement.

Management of the Anterior Cruciate Ligament-Injured Knee in the Skeletally Immature Athlete.

Intrasubstance tears of the anterior cruciate ligament (ACL) are being diagnosed with increasing frequency in the skeletally immature. Management options include nonoperative/ early surgical, or delayed surgical reconstruction. Nonoperative/delayed reconstruction results in worse functional outcomes than early reconstruction. Physicians are faced with a treatment dilemma; clinical and basic science studies have demonstrated risk of limb-length discrepancy and angular deformity with ACL reconstruction. Vertical drill tunnels decrease physeal damage and minimize growth deformity; however, this technique results in nonanatomic ACL graft placement. All-epiphyseal reconstruction avoids damage to the growth plate. These techniques are biomechanically superior to extraarticular and modified physeal-sparing procedures.

Human-mediated extirpation of the unique Chatham Islands sea lion and implications for the conservation management of remaining New Zealand sea lion populations.

While terrestrial megafaunal extinctions have been well characterized worldwide, our understanding of declines in marine megafauna remains limited. Here, we use ancient DNA analyses of prehistoric (<1450-1650 AD) sea lion specimens from New Zealand's isolated Chatham Islands to assess the demographic impacts of human settlement. These data suggest there was a large population of sea lions, unique to the Chatham Islands, at the time of Polynesian settlement. This distinct mitochondrial lineage became rapidly extinct within 200 years due to overhunting, paralleling the extirpation of a similarly large endemic mainland population. Whole mitogenomic analyses confirm substantial intraspecific diversity among prehistoric lineages. Demographic models suggest that even low harvest rates would likely have driven rapid extinction of these lineages. This study indicates that surviving Phocarctos populations are remnants of a once diverse and widespread sea lion assemblage, highlighting dramatic human impacts on endemic marine biodiversity. Our findings also suggest that Phocarctos bycatch in commercial fisheries may contribute to the ongoing population decline.

Iliopsoas: Pathology, Diagnosis, and Treatment.

Disorders of the iliopsoas can be a significant source of groin pain in the athletic population. Commonly described pathologic conditions include iliopsoas bursitis, tendonitis, impingement, and snapping. The first-line treatment for iliopsoas disorders is typically conservative, including activity modification, physical therapy, nonsteroidal anti-inflammatory drugs, and corticosteroid injections. Surgical treatment can be considered if the patient fails conservative measures and typically involves arthroscopic lengthening of the musculotendinous unit and treatment of concomitant intra-articular abnormality. Tendon release has been described: in the central compartment, in the peripheral compartment, and at the lesser trochanter, with similar outcomes observed between the techniques.

Invader or resident? Ancient-DNA reveals rapid species turnover in New Zealand little penguins.

The expansion of humans into previously unoccupied parts of the globe is thought to have driven the decline and extinction of numerous vertebrate species. In New Zealand, human settlement in the late thirteenth century AD led to the rapid demise of a distinctive vertebrate fauna, and also a number of 'turnover' events where extinct lineages were subsequently replaced by closely related taxa. The recent genetic detection of an Australian little penguin (Eudyptula novaehollandiae) in southeastern New Zealand may potentially represent an additional 'cryptic' invasion. Here we use ancient-DNA (aDNA) analysis and radiocarbon dating of pre-human, archaeological and historical Eudyptula remains to reveal that the arrival of E. novaehollandiae in New Zealand probably occurred between AD 1500 and 1900, following the anthropogenic decline of its sister taxon, the endemic Eudyptula minor. This rapid turnover event, revealed by aDNA, suggests that native species decline can be masked by invasive taxa, and highlights the potential for human-mediated biodiversity shifts.

Geographically contrasting biodiversity reductions in a widespread New Zealand seabird.

Unravelling prehistoric anthropogenic impacts on biodiversity represents a key challenge for biologists and archaeologists. New Zealand's endemic Stewart Island Shag (Leucocarbo chalconotus) comprises two distinct phylogeographic lineages, currently restricted to the country's south and southeast. However, fossil and archaeological remains suggest a far more widespread distribution at the time of Polynesian settlement ca. 1280 AD, encompassing much of coastal South Island. We used modern and ancient DNA, radiocarbon dating, and Bayesian modelling, to assess the impacts of human arrival on this taxon. Our analyses show that the southeast South Island (Otago) lineage was formerly widespread across coastal South Island, but experienced dramatic population extinctions, range retraction and lineage loss soon after human arrival. By comparison, the southernmost (Foveaux Strait) lineage has experienced a relatively stable demographic and biogeographic history since human arrival, retaining much of its mitochondrial diversity. Archaeological data suggest that these contrasting demographic histories (retraction vs. stability) reflect differential human impacts in mainland South Island vs. Foveaux Strait, highlighting the importance of testing for temporal and spatial variation in human-driven faunal declines.

Femoral Neck Stress Fractures and Imaging Features of Femoroacetabular Impingement.

BACKGROUND: Prior literature has suggested an association between the radiographic signs of femoroacetabular impingement (FAI) and femoral neck stress fractures (FNSF) or femoral neck stress reactions (FNSR). At the time of the writing of this article, no study has described the association of FAI and FNSF/FNSR along with the need for surgical intervention and outcomes. OBJECTIVE: To determine the prevalence of radiographic features of FAI in patients diagnosed with FNSF. DESIGN: Retrospective case series. SETTING: Tertiary care, institutional setting. PATIENTS: A medical records search program (Stanford Translational Research Integrated Database Environment, Stanford University, California) was used to retrospectively search for patients 18-40 years old with a history of FNSF or FNSR. The records were obtained from the period July 25, 2003, to September 23, 2011. METHODS: For assessment of risk factors, plain radiographs and magnetic resonance imaging studies were reviewed for features of cam or pincer FAI. Medical records were reviewed to determine whether patients required operative intervention. MAIN OUTCOME MEASURES: Incidence of abnormal alpha (α) angle, abnormal anterior offset ratio, abnormal femoral head-neck junction, coxa profunda, positive crossover sign, and abnormal lateral center-to-edge angle. RESULTS: Twenty-one female and 3 male participants (mean age 27 years, range 19-39 years) were identified with magnetic resonance imaging evidence of femoral neck stress injury. Cam morphology was seen in 10 patients (42%). Pincer morphology could be assessed in 18 patients, with coxa profunda in 14 (78%) and acetabular retroversion in 6 (14%). Features of combined pincer and cam impingement were observed in 4 patients (17%). Seven patients (29%) had operative intervention, with 3 (12%) requiring internal fixation of their femoral neck fractures, and all had radiographic evidence of fracture union after surgery. Four patients (17%) had persistent symptoms after healing of their FNSF with conservative treatment and eventually required surgery for FAI, 3 had no pain at final follow-up 1 year post-surgery, and one patient was lost to follow-up. CONCLUSION: The results of the current study suggest that patients in the general population with femoral neck stress injuries have a higher incidence of bony abnormalities associated with pincer impingement, including coxa profunda and acetabular retroversion, although it is unclear whether pincer FAI is a true risk factor in the development of FNSF.

Correlation of meniscal and articular cartilage injuries in children and adolescents with timing of anterior cruciate ligament reconstruction.

BACKGROUND: In pediatric patients, anterior cruciate ligament (ACL) reconstruction is controversial; however, delaying surgery until skeletal maturity is complete may increase the risk of secondary meniscal and articular cartilage injury. PURPOSE: To assess the risk of meniscal and chondral injuries with delay of ACL reconstruction. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Records were reviewed in patients younger than 17 years (median age, 14 years) who had ACL reconstruction. Patients were consecutively enrolled and assigned to 1 of 3 surgical groups based on timing of surgery: acute (<6 weeks after surgery), subacute (6-12 weeks), or chronic (>3 months). The type and grade of meniscal injuries was documented according to the International Society of Arthroscopy, Knee Surgery, and Orthopaedic Sports Medicine (ISAKOS) meniscal classification criteria. International Cartilage Repair Society (ICRS) criteria were used to document location and grade of chondral injuries. Associations between patient characteristics and meniscal injury were tested using rank sum and chi-square tests. Regression analyses were conducted to model incidence and severity of lateral and medial meniscal tears. There were 130 patients who had 135 ACL reconstructions between the years of 2000 and 2012. RESULTS: Sixty-two ACL injuries were treated acutely, 37 were subacute, and 36 were chronic. Meniscal injuries (n = 112) included 70 lateral and 42 medial tears. Time to surgery had bivariate association with lateral and medial meniscal tears (P = .016 and .007, respectively). Independent risk factors for incidence of lateral meniscal tears were younger age (P = .028) and return to sports activities before surgery (P = .007). Patients with 1 episode of instability had 3-fold higher odds of higher grade lateral meniscal tear (95% CI, 1.30-7.60). Compared with acute reconstruction, subacute and chronic reconstruction patients had 1.45 and 2.82 times higher odds, respectively, of lateral meniscal tear severity (P = .12). Independent risk factors for incidence of medial meniscal tears were female sex (P = .03), older age (P = .01), and any episode of instability (P = .01). Adjusted odds ratio for medial meniscal tear was 4.7 for an instability episode (vs no episode; P = .01). Adjusted odds ratio for increased severity of medial meniscal tears included any instability episode, 5.6 (P < .01); playing sports before reconstruction, 15.2 (P < .01); and time to surgery greater than 3 months, 4.3 (P = .046). Seventeen patients had 23 chondral injuries. The risk factors for chondral injury included increased time to surgery (P = .005) and any instability episode (P = .001). For increased grade of chondral injury, risk factors were time to surgery (P ≤ .001) and any instability episode (P = .003). CONCLUSION: Delayed ACL reconstruction increased the risks of secondary meniscal and chondral injuries in this population of pediatric patients.

Extinction and recolonization of coastal megafauna following human arrival in New Zealand.

Extinctions can dramatically reshape biological communities. As a case in point, ancient mass extinction events apparently facilitated dramatic new evolutionary radiations of surviving lineages. However, scientists have yet to fully understand the consequences of more recent biological upheaval, such as the megafaunal extinctions that occurred globally over the past 50 kyr. New Zealand was the world's last large landmass to be colonized by humans, and its exceptional archaeological record documents a vast number of vertebrate extinctions in the immediate aftermath of Polynesian arrival approximately AD 1280. This recently colonized archipelago thus presents an outstanding opportunity to test for rapid biological responses to extinction. Here, we use ancient DNA (aDNA) analysis to show that extinction of an endemic sea lion lineage (Phocarctos spp.) apparently facilitated a subsequent northward range expansion of a previously subantarctic-limited lineage. This finding parallels a similar extinction-replacement event in penguins (Megadyptes spp.). In both cases, an endemic mainland clade was completely eliminated soon after human arrival, and then replaced by a genetically divergent clade from the remote subantarctic region, all within the space of a few centuries. These data suggest that ecological and demographic processes can play a role in constraining lineage distributions, even for highly dispersive species, and highlight the potential for dynamic biological responses to extinction.

Hip-femoral acetabular impingement.

Magnetic resonance imaging (MRI) has become a valuable technology for the diagnosis and treatment of femoroacetabular impingement (FAI). This article reviews the basic pathophysiology of FAI, as well as the techniques and indications for MRI and magnetic resonance arthrography. Normal MRI anatomy of the hip and pathologic MRI anatomy associated with FAI are also discussed. Several case examples are presented demonstrating the diagnosis and treatment of FAI.

Biomechanical evaluation of physeal-sparing fixation methods in tibial eminence fractures.

BACKGROUND: Tibial eminence fractures occur most commonly in skeletally immature children. Several techniques using physeal-sparing fracture fixation have been described, but their structural properties have not been evaluated. PURPOSE: To determine the strength and resistance to displacement of physeal-sparing techniques used to fix tibial eminence fractures. STUDY DESIGN: Controlled laboratory study. METHODS: Skeletally immature porcine knees were randomized into 4 treatment groups: (1) ultra-high molecular weight polyethylene suture-suture button (UHMWPE/SB), (2) suture anchor, (3) polydioxanone suture-suture button (PDS/SB), and (4) screw fixation. A prospective analysis of bone mineral density using dual-energy x-ray absorptiometry was performed on all specimens. Fracture fragments were created in a standardized manner and measured for size comparison. After fracture fixation, biomechanical testing was performed with cyclical and load-to-failure protocols by loading the tibia with an anterior shear force. RESULTS: In load-to-failure testing, screw fixation had a significantly lower median peak failure load (186.4 N; lower quartile [LQ], 158.4 N; upper quartile [UQ], 232.6 N) than did UHMWPE/SB (465.8 N; LQ, 397.8 N; UQ, 527.8 N), suture anchors (440.5 N; LQ, 323.0 N; UQ, 562.3 N), and PDS/SB (404.3 N; LQ, 385.9 N; UQ, 415.6 N). UHMWPE/SB demonstrated a significantly higher median yield load (465.8 N; LQ, 397.8 N; UQ, 527.8 N) than did PDS/SB (306.7 N; LQ, 271.4, N; UQ, 405.7 N) and screw fixation (179.0 N; LQ, 120.2 N; UQ, 232.5 N). During cyclical testing, screw fixation demonstrated significantly lower percentage survival of specimens (0%) compared with the other groups (UHMWPE/SB, 100%; suture anchor, 78%; PDS/SB, 78%). After 1000 cycles of loading, PDS/SB fixation had significantly more median creep (6.76 mm; LQ, 6.34 mm; UQ, 8.28 mm) than did UHMWPE/SB (4.43 mm; LQ, 3.80 mm; UQ, 4.73 mm) and suture anchor fixation (3.06 mm; LQ, 2.59 mm; UQ, 4.28 mm). The lowest median stiffness was observed in the PDS/SB group (48.6 N/mm; LQ, 45.3 N/mm; UQ, 54.2 N/mm). UHMWPE/SB fixation demonstrated a significantly higher median peak failure load after cyclic testing (469.0 N; LQ, 380.6 N; UQ, 507.2 N) than did PDS/SB (237.7 N; LQ, 197.3 N; UQ, 298.3 N) and screw fixation (132.4 N; LQ, 123.7 N; UQ, 180.9 N). Suture anchor fixation had significantly more variance, as demonstrated by width of interquartile range, in peak failure load, yield load, and creep than did other techniques. CONCLUSION: Physeal-sparing fixation of tibial eminence fractures with UHMWPE suture-suture button is biomechanically superior to both PDS suture-suture button and a single screw at the time of surgery and provides more consistent fixation than do suture anchors. CLINICAL RELEVANCE: Suture anchors provide inconsistent fixation for tibial eminence fractures.

Operative Fixation of Chondral Loose Bodies in Osteochondritis Dissecans in the Knee: A Report of 5 Cases.

BACKGROUND: Osteochondritis dissecans (OCD) can progress to loose body formation, with or without subchondral bone attachment to the lesion. The efficacy of internal fixation of chondral loose bodies has not been determined. HYPOTHESIS: Operative fixation of cartilaginous loose bodies would result in (1) healed OCD at second-look arthroscopy, (2) restored cartilage appearance on magnetic resonance imaging (MRI), and (3) nearly normal knee function, as determined by patient-reported outcome scores. STUDY DESIGN: Retrospective case series; Level of evidence, 4. METHODS: Five patients who underwent cartilaginous loose body fixation were identified. Lesions were located on the lateral trochlea (n = 2) and medial femoral condyle (n = 3) (mean size, 2.5 cm(2)). Loose bodies were reattached with compression screws through mini-arthrotomy or arthroscopy. Patients were nonweightbearing for 12 weeks postoperatively. After 12 weeks, screws were removed arthroscopically, and OCD stability was evaluated. Three patients underwent MRI to determine articular cartilage status. Images were evaluated using the magnetic resonance observation of cartilage repair tissue (MOCART) score. Patients were interviewed and completed the Knee injury and Osteoarthritis Outcome Score (KOOS) questionnaire. RESULTS: Four patients had stable lesions at 12 weeks after surgery. One patient had slight motion to one-third of the lesion and stability to the remaining two-thirds. Three patients underwent an MRI. The mean time from surgery to MRI was 3.1 years. Mean MOCART score was 72.0 ± 10.4. One patient required repeat arthroscopy 1 year after initial fixation for debridement and arthroscopic drilling of an incompletely healed area of the lesion. Four patients completed the KOOS questionnaire. The mean time to KOOS completion was 4.6 years. Mean KOOS subscales for knee pain (91.0 ± 8.9), knee symptoms (83.0 ± 7.9), and function in activities of daily living (91.9 ± 10.6) were similar to published age-matched controls; however, scores for sports and recreation function (70.0 ± 17.8) and knee-related quality of life (67.2 ± 12.9) were lower. CONCLUSION: Operative fixation of chondral loose bodies, without macroscopically visible subchondral bone attachment, resulted in lesion stability at second-look arthroscopy. At final follow-up, patients had no substantial pain and normal function in activities of daily life compared with controls; however, knee-related quality of life and sport and recreation function were reduced, and 1 patient required reoperation for an unhealed portion of the lesion.

Tangled trees: the challenge of inferring species trees from coalescent and noncoalescent genes.

Phylogenies based on different genes can produce conflicting phylogenies; methods that resolve such ambiguities are becoming more popular, and offer a number of advantages for phylogenetic analysis. We review so-called species tree methods and the biological forces that can undermine them by violating important aspects of the underlying models. Such forces include horizontal gene transfer, gene duplication, and natural selection. We review ways of detecting loci influenced by such forces and offer suggestions for identifying or accommodating them. The way forward involves identifying outlier loci, as is done in population genetic analysis of neutral and selected loci, and removing them from further analysis, or developing more complex species tree models that can accommodate such loci.