Yi-Meng Yen

Outcomes following hip arthroscopy for femoroacetabular impingement with associated chondrolabral dysfunction: MINIMUM TWO-YEAR FOLLOW-UP

Over an eight-month period we prospectively enrolled 122 patients who underwent arthroscopic surgery of the hip for femoroacetabular impingement and met the inclusion criteria for this study. Patients with bilateral hip arthroscopy, avascular necrosis and previous hip surgery were excluded. Ten patients refused to participate leaving 112 in the study. There were 62 women and 50 men. The mean age of the patients was 40.6 yrs (95% confidence interval (CI) 37.7 to 43.5). At arthroscopy, 23 patients underwent osteoplasty only for cam impingement, three underwent rim trimming only for pincer impingement, and 86 underwent both procedures for mixed-type impingement. The mean follow-up was 2.3 years (2.0 to 2.9). The mean modified Harris hip score (HHS) improved from 58 to 84 (mean difference = 24 (95% CI 19 to 28)) and the median patient satisfaction was 9 (1 to 10). Ten patients underwent total hip replacement at a mean of 16 months (8 to 26) after arthroscopy. The predictors of a better outcome were the pre-operative modified HHS (p = 0.018), joint space narrowing >or= 2 mm (p = 0.005), and repair of labral pathology instead of debridement (p = 0.032). Hip arthroscopy for femoroacetabular impingement, accompanied by suitable rehabilitation, gives a good short-term outcome and high patient satisfaction.

Early outcomes after hip arthroscopy for femoroacetabular impingement in the athletic adolescent patient: a preliminary report.

Background: Hip arthroscopy is becoming a more popular method of treatment of pediatric hip disorders. We report on the treatment of femoroacetabular impingement (FAI) in the adolescent population. Methods: Between March 2005 and May 2006, 16 patients (aged 16 years or younger) underwent hip arthroscopy for FAI. There were 14 female adolescents and 2 male adolescents, with 1 patient undergoing a bilateral procedure. Five patients had isolated pincer impingement, 2 had isolated cam impingement, and 9 had mixed pathology. All patients had labral pathology. Seven patients were treated with suture anchor repair of the labrum and 9 with partial labral debridement. Subjective data were collected from each patient during their initial visit and at follow-up after surgery. Subjective data included the modified Harris hip score (MHHS), patient satisfaction, and hip outcome score (HOS) activities of daily living (ADL), and sports subscales. Results: The mean age at the time of arthroscopy was 15 years old (range, 11-16 years). The mean preoperative MHHS was 55 (range, 33-70), HOS ADL was 58 (range, 38-75), and HOS sport was 33 (range, 0-78). The mean time from injury to surgery was 10.6 months (range, 6 weeks-30 months). The mean time to follow-up was 1.36 years (range, 1-2 years). The mean postoperative MHHS improved 35 points to 90 (range, 70-100; P = 0.005), postoperative HOS ADL improved 36 points to 94 (range, 74-100; P = 0.001), and postoperative HOS sport score improved 56 points to 89 (range, 58-100; P = 0.001). The mean patient satisfaction score was 9 (range, 9-10). Conclusions: Hip arthroscopy for FAI in the adolescent population produces excellent improvement in function and a high level of patient satisfaction in the short-term. Level of Evidence Level IV, case series.

Solution structure of the HMG protein NHP6A and its interaction with DNA reveals the structural determinants for non-sequence-specific binding.

NHP6A is a chromatin‐associated protein from Saccharomyces cerevisiae belonging to the HMG1/2 family of non‐specific DNA binding proteins. NHP6A has only one HMG DNA binding domain and forms relatively stable complexes with DNA. We have determined the solution structure of NHP6A and constructed an NMR‐based model structure of the DNA complex. The free NHP6A folds into an L‐shaped three α‐helix structure, and contains an unstructured 17 amino acid basic tail N‐terminal to the HMG box. Intermolecular NOEs assigned between NHP6A and a 15 bp 13C, 15N‐labeled DNA duplex containing the SRY recognition sequence have positioned the NHP6A HMG domain onto the minor groove of the DNA at a site that is shifted by 1 bp and in reverse orientation from that found in the SRY–DNA complex. In the model structure of the NHP6A–DNA complex, the N‐terminal basic tail is wrapped around the major groove in a manner mimicking the C‐terminal tail of LEF1. The DNA in the complex is severely distorted and contains two adjacent kinks where side chains of methionine and phenylalanine that are important for bending are inserted. The NHP6A–DNA model structure provides insight into how this class of architectural DNA binding proteins may select preferential binding sites.

The S. cerevisiae architectural HMGB protein NHP6A complexed with DNA: DNA and protein conformational changes upon binding

NHP6A is a non-sequence-specific DNA-binding protein from Saccharomyces cerevisiae which belongs to the HMGB protein family. Previously, we have solved the structure of NHP6A in the absence of DNA and modeled its interaction with DNA. Here, we present the refined solution structures of the NHP6A-DNA complex as well as the free 15bp DNA. Both the free and bound forms of the protein adopt the typical L-shaped HMGB domain fold. The DNA in the complex undergoes significant structural rearrangement from its free form while the protein shows smaller but significant conformational changes in the complex. Structural and mutational analysis as well as comparison of the complex with the free DNA provides insight into the factors that contribute to binding site selection and DNA deformations in the complex. Further insight into the amino acid determinants of DNA binding by HMGB domain proteins is given by a correlation study of NHP6A and 32 other HMGB domains belonging to both the DNA-sequence-specific and non-sequence-specific families of HMGB proteins. The resulting correlations can be rationalized by comparison of solved structures of HMGB proteins.

Mechanism for specificity by HMG-1 in enhanceosome assembly.

ABSTRACT Assembly of enhanceosomes requires architectural proteins to facilitate the DNA conformational changes accompanying cooperative binding of activators to a regulatory sequence. The architectural protein HMG-1 has been proposed to bind DNA in a sequence-independent manner, yet, paradoxically, it facilitates specific DNA binding reactions in vitro. To investigate the mechanism of specificity we explored the effect of HMG-1 on binding of the Epstein-Barr virus activator ZEBRA to a natural responsive promoter in vitro. DNase I footprinting, mutagenesis, and electrophoretic mobility shift assay reveal that HMG-1 binds cooperatively with ZEBRA to a specific DNA sequence between two adjacent ZEBRA recognition sites. This binding requires a strict alignment between two adjacent ZEBRA sites and both HMG boxes of HMG-1. Our study provides the first demonstration of sequence-dependent binding by a nonspecific HMG-box protein. We hypothesize how a ubiquitous, nonspecific architectural protein can function in a specific context through the use of rudimentary sequence recognition coupled with cooperativity. The observation that an abundant architectural protein can bind DNA cooperatively and specifically has implications towards understanding HMG-1s role in mediating DNA transactions in a variety of enzymological systems.

Propionobacter acnes Infection as an Occult Cause of Postoperative Shoulder Pain: A Case Series

BackgroundInfections after shoulder surgery are potentially devastating complications. Propionibacterium acnes is recognized as a causal agent in shoulder infections. The clinical presentation is usually insidious and nonspecific, but a P. acnes infection could be an occult cause of postoperative shoulder pain.Questions/purposesWhat are the clinical and microbiologic characteristics of a postsurgical P. acnes shoulder infection and how should it be addressed?Patients and MethodsTen patients with an average age of 57 years presented with P. acnes postsurgical shoulder infection. Clinical infection signs and surgical history were assessed and joint aspirates and tissue biopsy specimens were obtained. Diagnosis was confirmed by microbiologic cultures.ResultsAt the time of confirmation of the diagnosis, clinical signs of infection were absent. C-reactive protein and erythrocyte sedimentation rates were inconsistently elevated. Cultures took a mean 7 days to confirm organism growth. The average time from surgery to diagnosis of infection was 1.8 years (range, 0.07–8.0 years). All patients underwent irrigation and débridement and were treated with antibiotics for 6 weeks.ConclusionsP. acnes shoulder infections should be considered as a cause for persistent, unexplained shoulder pain. Shoulder aspirations and tissue samples should be obtained. Surgical débridement and intravenous antibiotics are necessary treatment modalities.Level of EvidenceLevel IV, Prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Chondral lesions of the hip: microfracture and chondroplasty.

Hip arthroscopy has become increasingly popular over the past several years as the techniques have evolved to be able to address both the peripheral and central compartments of the hip. The main indications for hip arthroscopy 10 years ago were diagnostic and debridement procedures such as removal of loose bodies, labral resection, synovectomy, and cartilage debridement. Advances in this field have now expanded to include reconstruction and repair of the labrum, recontouring of the acetabulum and head-neck junction, cartilage salvage, and repair and releases of the tendons around the hip joint. We detail in this article chondral injuries that occur in the hip joint and arthroscopic procedures to address these issues. We routinely perform chondroplasty in cases where there is a partial thickness tear of articular cartilage. Full thickness defects are addressed with microfracture which follows closely the guidelines established for the knee. As our understanding of chondral injuries and their causes grows, future efforts will focus on prevention.

Determinants of DNA Binding and Bending by theSaccharomyces cerevisiae High Mobility Group Protein NHP6A That Are Important for Its Biological Activities ROLE OF THE UNIQUE N TERMINUS AND PUTATIVE INTERCALATING METHIONINE

The non-histone proteins 6A/B (NHP6A/B) ofSaccharomyces cerevisiae are high mobility group proteins that bind and severely bend DNA of mixed sequence. They exhibit high affinity for linear DNA and even higher affinity for microcircular DNA. The 16-amino acid basic segment located N-terminal to the high mobility group domain is required for stable complex formation on both linear and microcircular DNA. Although mutants lacking the N terminus are able to promote microcircle formation and Hin invertasome assembly at high protein concentrations, they are unable to form stable complexes with DNA, co-activate transcription, and complement the growth defect ofΔnhp6a/b mutants. A basic patch between amino acids 13 and 16 is critical for these activities, and a second basic patch between residues 8 and 10 is required for the formation of monomeric complexes with linear DNA. Mutational analysis suggests that proline 18 may direct the path of the N-terminal arm to facilitate DNA binding, whereas the conserved proline at position 21, tyrosine 28, and phenylalanine 31 function to maintain the tertiary structure of the high mobility group domain. Methionine 29, which may intercalate into DNA, is essential for NHP6A-induced microcircle formation of 75-bp but not 98-bp fragments in vitro, and for full growth complementation of Δnhp6a/b mutants in vivo.

Lateral entry compared with medial and lateral entry pin fixation for completely displaced supracondylar humeral fractures in children. Surgical technique.

BACKGROUND Closed reduction and percutaneous pin fixation is the treatment of choice for completely displaced (type-III) extension supracondylar fractures of the humerus in children, although controversy persists regarding the optimal pin-fixation technique. The purpose of this study was to compare the efficacy of lateral entry pin fixation with that of medial and lateral entry pin fixation for the operative treatment of completely displaced extension supracondylar fractures of the humerus in children. METHODS This prospective, randomized clinical trial had sufficient power to detect a 10% difference in the rate of loss of reduction between the two groups. The techniques of lateral entry and medial and lateral entry pin fixation were standardized in terms of the pin location, the pin size, the incision and position of the elbow used for medial pin placement, and the postoperative course. The primary study end points were a major loss of reduction and iatrogenic ulnar nerve injury. Secondary study end points included radiographic measurements, clinical alignment, Flynn grade, elbow range of motion, function, and complications. RESULTS The lateral entry group (twenty-eight patients) and the medial and lateral entry group (twenty-four patients) were similar in terms of mean age, sex distribution, and preoperative displacement, comminution, and associated neurovascular status. No patient in either group had a major loss of reduction. There was no significant difference between the rates of mild loss of reduction, which occurred in six of the twenty-eight patients treated with lateral entry and one of the twenty-four treated with medial and lateral entry (p = 0.107). There were no cases of iatrogenic ulnar nerve injury in either group. There were also no significant differences (p > 0.05) between groups with respect to the Baumann angle, change in the Baumann angle, humerocapitellar angle, change in the humerocapitellar angle, Flynn grade, carrying angle, elbow flexion, elbow extension, total elbow range of motion, return to function, or complications. CONCLUSIONS With use of the specific techniques employed in this study, both lateral entry pin fixation and medial and lateral entry pin fixation are effective in the treatment of completely displaced (type-III) extension supracondylar fractures of the humerus in children.

Is intraarticular pathology common in patients with hip dysplasia undergoing periacetabular osteotomy

BackgroundPeriacetabular osteotomy (PAO) enables correction of bony acetabular deficiency in the setting of hip dysplasia. Patients with insufficient acetabular coverage often have intraarticular pathology, but the degree of this pathology has been incompletely characterized. We have used arthroscopy as an adjunct to PAO to further delineate intraarticular pathology in patients with hip dysplasia with mechanical symptoms.Questions/purposesWe documented the arthroscopic incidence of (1) femoral and acetabular chondral pathology, (2) femoral neck cam lesions, and (3) internal snapping or ligamentum teres pathology among patients having arthroscopy before PAO.MethodsWe reviewed all 16 patients (17 hips; mean age at surgery, 21 years; range, 12–33 years) with hip dysplasia who underwent PAOs and concomitant hip arthroscopy at our institutions from October 2010 to March 2012. During this period, 80 patients underwent PAOs, making the arthroscopic cohort 21% of the total cohort. Indications for concomitant hip arthroscopy were mechanical symptoms consistent with labral pathology identified on MRI. We documented pathology involving the labrum, chondral surface, ligamentum teres, cam deformity, and psoas tendon.ResultsArthroscopy revealed significant intraarticular pathology in all patients. Fourteen hips had anterosuperior labral tears, and three hips had preoperative findings of internal snapping hip. Eleven hips had femoral cam-type lesions in addition to dysplasia, and 16 hips had articular chondral injury. Two hips had full-thickness ligamentum tears, and 13 hips had partial-thickness tears.ConclusionsIntraarticular pathology at the time of PAO is common. Future studies are needed to rigorously address the use of arthroscopic intervention during PAO and the impact on clinical outcome compared to PAO alone.Level of EvidenceLevel IV, diagnostic study. See Instructions for Authors for a complete description of levels of evidence.