Clinical and Radiographic Outcomes of the Ream-and-Run Procedure for Primary Glenohumeral Arthritis

BACKGROUND

The ream-and-run procedure can provide improvement in shoulder function and comfort for selected patients with primary glenohumeral arthritis who wish to avoid a prosthetic glenoid component. The purpose of this study was to evaluate factors associated with medialization of the humeral head after this procedure as well as the relationship of medialization to the clinical outcome.

METHODS

We collected patient, shoulder, and procedure characteristics along with Simple Shoulder Test (SST) scores before surgery and at the time of follow-up. Medialization was determined by comparing the position of the humeral head prosthesis in relation to the scapula on postoperative baseline radiographs made within 6 weeks after surgery with that on comparable follow-up radiographs made ≥18 months after surgery.

RESULTS

Two-year clinical outcomes were available for 101 patients (95% were male). Comparable radiographs at postoperative baseline and follow-up evaluations were available for 50 shoulders. For all patients, the mean SST score (and standard deviation) increased from 4.9 ± 2.8 preoperatively to 10.3 ± 2.4 at the latest follow-up (p < 0.001). Significant clinical improvement was observed for glenoid types A2 and B2. Shoulders with a type-A2 glenoid morphology, with larger preoperative scapular body-glenoid angles, and with lower preoperative SST scores, were associated with the greatest clinical improvement. Clinical outcome was not significantly associated with the amount of medialization.

CONCLUSIONS

The ream-and-run procedure can be an effective treatment for advanced primary glenohumeral osteoarthritis in active patients. Further study will be necessary to determine whether medialization affects the clinical outcome with follow-up of >2 years.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

The shape of the one-dimensional phylogenetic likelihood function

By fixing all parameters in a phylogenetic likelihood model except for one branch length, one obtains a one-dimensional likelihood function. In this work, we introduce a mathematical framework to characterize the shapes of such one-dimensional phylogenetic likelihood functions. This framework is based on analyses of algebraic structures on the space of all frequency patterns with respect to a polynomial representation of thspace likelihood functions. Using this framework, we provide conditions under which the one-dimensional phylogenetic likelihood functions are guaranteed to have at most one stationary point, and this point is the maximum likelihood branch length. These conditions are satisfied by common simple models including all binary models, the Jukes-Cantor model and the Felsenstein 1981 model. We then prove that for the simplest model that does not satisfy our conditions, namely, the Kimura 2-parameter model, the one-dimensional likelihood functions may have multiple stationary points. As a proof of concept, we construct a non-degenerate example in which the phylogenetic likelihood function has two local maxima and a local minimum. To construct such examples, we derive a general method of constructing a tree and sequence data with a specified frequency pattern at the root. We then extend the result to prove that the space of all rescaled and translated one-dimensional phylogenetic likelihood functions under the Kimura 2-parameter model is dense in the space of all non-negative continuous functions on [0, ∞) with finite limits. These results indicate that one-dimensional likelihood functions under advanced evolutionary models can be more complex than it is typically assumed by phylogenetic inference algorithms; however, these complexities can be effectively captured by the Kimura 2-parameter model.

Treatment of irreparable cuff tears with smoothing of the humeroscapular motion interface without acromioplasty

PURPOSE

We sought to determine whether shoulders with irreparable rotator cuff tears and retained active elevation can be durably improved using a conservative surgical procedure that smoothes the interface between the proximal humeral convexity and the concave undersurface of the coracoacromial arch followed by immediate range of motion exercises.

METHODS

We reviewed 151 patients with a mean age of 63.4 (range 40-90) years at a mean of 7.3 (range 2-19) years after this surgery.

RESULTS

In 77 shoulders with previously unrepaired irreparable tears, simple shoulder test (SST) scores improved from an average of 4.6 (range 0-12) to 8.5 (range 1-12) (p < 0.001). Fifty-four patients (70%) improved by at least the minimally clinically important difference (MCID) of 2 SST points. For 74 shoulders with irreparable failed prior repairs, SST scores improved from 4.0 (range 0-11) to 7.5 (range 0-12) (p < 0.001). Fifty-four patients (73%) improved by the MCID of 2 SST points.

CONCLUSION

Smoothing of the humeroscapular interface can improve symptomatic shoulders with irreparable cuff tears and retained active elevation. This conservative procedure offers an alternative to more complex procedures in the management of irreparable rotator cuff tears.

LEVEL OF EVIDENCE

Level IV.

Relationship Between Patient-Reported Assessment of Shoulder Function and Objective Range-of-Motion Measurements

BACKGROUND

Assessment of function is the cornerstone of clinical shoulder research. This purpose of this study was to answer 3 relevant questions: How does subjective patient assessment of shoulder function correlate with objectively measured active shoulder range of motion? What is the difference in active motion between shoulders that can and those that cannot be used to perform each of the functions of the Simple Shoulder Test (SST)? Does the relationship between subjective and objective assessment of shoulder function differ between male and female patients?

METHODS

We analyzed the relationship between objective range-of-motion measurements recorded by the observer-independent Kinect motion capture system and SST patient self-assessments of shoulder function of 74 male and 30 female patients with osteoarthritis.

RESULTS

There was poor correlation between objective measurements of active abduction and total SST scores of osteoarthritic shoulders of patients seen before shoulder surgery: the coefficients of determination (R) were 0.29 for the osteoarthritic shoulders of women and 0.25 for those of men. The relationships between active abduction and total SST score were closer for the contralateral shoulders (R = 0.54 for women and R = 0.46 for men). The difference in active abduction between the osteoarthritic shoulders that allowed and those that did not allow the patient to perform the individual SST functions was significant (p < 0.05) for only 4 of the 12 functions in the female group and 5 of 12 in the male group because of the highly variable relationship between self-assessed function and active abduction. In contrast, when the contralateral shoulders were assessed, this difference was found to be significant for 10 of the 12 functions in the female group and all 12 of the functions in the male group. The relationship between objective motion and subjective function did not differ significantly between male and female subjects.

CONCLUSIONS

The self-assessed function of osteoarthritic shoulders of women and men is only partially determined by the active range of abduction. Both subjective and objective measurements are important in characterizing the clinical status of shoulders. Studies of treatment outcomes should include separate assessments of these 2 complementary aspects of shoulder function.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Characterizing the Propionibacterium Load in Revision Shoulder Arthroplasty: A Study of 137 Culture-Positive Cases

BACKGROUND

Propionibacterium is commonly recovered from explants or surrounding tissues in revision shoulder arthroplasty. Rather than attempting to differentiate a true infection from a false-positive result on the basis of the number of positive cultures, we characterized the amount of these bacteria in each specimen and shoulder.

METHODS

The study included 137 revision shoulder arthroplasties from which a minimum of 4 specimens had been submitted for culture and at least 1 was positive for Propionibacterium. Standard microbiology procedures were used to assign a semiquantitative value (0.1, 1, 2, 3, or 4), called the Specimen Propi Value, to the amount of growth in each specimen. The sum of the Specimen Propi Values for each shoulder was defined as the Shoulder Propi Score, which was then divided by the total number of specimens to calculate the Average Shoulder Propi Score.

RESULTS

The number and percentage of positive specimen-specific cultures (of material obtained from the stem explant, head explant, glenoid explant, humeral membrane, collar membrane, other soft tissue, fluid, or other) per shoulder ranged from 1 to 6 and 14% to 100%. A high percentage of specimens (mean, 43%; median, 50%) from the culture-positive shoulders showed no growth. Only 32.6% of the fluid cultures were positive in comparison with 66.5% of the soft-tissue cultures and 55.6% of the cultures of explant specimens. The average Specimen Propi Value (and standard deviation) for fluid specimens (0.35 ± 0.89) was significantly lower than those for the soft-tissue (0.92 ± 1.50) and explant (0.66 ± 0.90) specimens (p < 0.001). The Shoulder Propi Score was significantly higher in men (3.56 ± 3.74) than in women (1.22 ± 3.11) (p < 0.001). Similarly, men had a significantly higher Average Shoulder Propi Score (0.53 ± 0.51) than women (0.19 ± 0.43) (p < 0.001).

CONCLUSIONS

This investigation suggests that Propionibacterium is unevenly distributed within culture-positive revised shoulders. As a result, the specimen number and source (explant, soft tissue, or fluid) have major influences on the culture results for a revised shoulder arthroplasty. We found no evidence that suggested useful threshold values for defining a true infection.

LEVEL OF EVIDENCE

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Single-Stage Revision Is Effective for Failed Shoulder Arthroplasty with Positive Cultures for Propionibacterium

BACKGROUND

Revision shoulder arthroplasties are often culture-positive for Propionibacterium. This study tests the hypothesis that the functional outcomes of revising Propionibacterium culture-positive failed arthroplasties with a single-stage revision and immediate antibiotic therapy are not inferior to the clinical outcomes of revising failed shoulder arthroplasties that are not culture-positive.

METHODS

Fifty-five shoulders without obvious clinical evidence of infection had a single-stage revision arthroplasty. The patient self-assessed functional outcomes for shoulders with ≥2 positive cultures for Propionibacterium (the culture-positive group) were compared with shoulders with no positive cultures or only 1 positive culture (the control group).

RESULTS

The culture-positive group had 89% male patients, with a mean age (and standard deviation) of 63.5 ± 7.2 years. The mean Simple Shoulder Test (SST) scores for the 27 culture-positive shoulders improved from 3.2 ± 2.8 points before the surgical procedure to 7.8 ± 3.3 points at a mean follow-up of 45.8 ± 11.7 months after the surgical procedure (p < 0.001), a mean improvement of 49% of the maximum possible improvement. The control group had 39% male patients, with a mean age of 67.1 ± 8.1 years. The mean SST scores for the 28 control shoulders improved from 2.6 ± 1.9 points preoperatively to 6.1 ± 3.4 points postoperatively at a mean follow-up of 49.6 ± 11.8 months (p < 0.001), a mean improvement of 37% of the maximum possible improvement. Subsequent procedures for persistent pain or stiffness were required in 3 patients (11%) in the culture-positive group and in 3 patients (11%) in the control group; none of the revisions were culture-positive. Fourteen patients reported side effects to antibiotics.

CONCLUSIONS

Clinical outcomes after single-stage revision for Propionibacterium culture-positive shoulders were at least as good as the outcomes in revision procedures for control shoulders. Two-stage revision procedures may not be necessary in the management of these cases. Patients should be educated with regard to potential antibiotic side effects.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Management of intraoperative posterior decentering in shoulder arthroplasty using anteriorly eccentric humeral head components

BACKGROUND

Posterior humeral decentering presents a challenge in glenohumeral arthroplasty. Soft tissue releases and osteophyte resection can lead to intraoperative decentering not evident preoperatively. Inferior outcomes result if decentering is not addressed as a part of the arthroplasty. When there is >50% posterior subluxation of the humeral head on passive elevation of the arm at surgery, we have used an anteriorly eccentric humeral head component to improve centering of the humeral articular surface on the glenoid.

METHODS

We reviewed the 2-year outcomes for 33 shoulder arthroplasties in which anteriorly eccentric humeral heads were used to manage posterior decentering identified at surgery. Rotator interval plication was performed in 16 cases as an adjunctive stabilizing procedure. Shoulders were evaluated preoperatively and postoperatively with the Simple Shoulder Test (SST). Radiographic centering was characterized before surgery and at follow-up on standardized axillary radiographs with the arm held in a position of functional elevation.

RESULTS

With the anteriorly eccentric head component, preoperative radiographic humeral decentering was reduced from 10.4% ± 7.9% to 0.9% ± 2.3% postoperatively (P < .001). SST scores improved from 4.8 ± 2.3 to 10.0 ± 2.3 (P < .001). Preoperative posterior humeral head decentering did not correlate with preoperative glenoid version. Glenoid retroversion was 19.8° ± 8.9° preoperatively and 15.5° ± 7.5° postoperatively.

CONCLUSIONS

Posterior decentering identified at surgery when standard trial components are in place can be addressed by replacing the anatomic humeral head with an anteriorly eccentric humeral head component.

What Factors are Predictive of Patient-reported Outcomes? A Prospective Study of 337 Shoulder Arthroplasties

BACKGROUND

Although shoulder arthroplasties generally are effective in improving patients' comfort and function, the results are variable for reasons that are not well understood.

QUESTIONS/PURPOSES

We posed two questions: (1) What factors are associated with better 2-year outcomes after shoulder arthroplasty? (2) What are the sensitivities, specificities, and positive and negative predictive values of a multivariate predictive model for better outcome?

METHODS

Three hundred thirty-nine patients having a shoulder arthroplasty (hemiarthroplasty, arthroplasty for cuff tear arthropathy, ream and run arthroplasty, total shoulder or reverse total shoulder arthroplasty) between August 24, 2010 and December 31, 2012 consented to participate in this prospective study. Two patients were excluded because they were missing baseline variables. Forty-three patients were missing 2-year data. Univariate and multivariate analyses determined the relationship of baseline patient, shoulder, and surgical characteristics to a "better" outcome, defined as an improvement of at least 30% of the maximal possible improvement in the Simple Shoulder Test. The results were used to develop a predictive model, the accuracy of which was tested using a 10-fold cross-validation.

RESULTS

After controlling for potentially relevant confounding variables, the multivariate analysis showed that the factors significantly associated with better outcomes were American Society of Anesthesiologists Class I (odds ratio [OR], 1.94; 95% CI, 1.03-3.65; p = 0.041), shoulder problem not related to work (OR, 5.36; 95% CI, 2.15-13.37; p < 0.001), lower baseline Simple Shoulder Test score (OR, 1.32; 95% CI, 1.23-1.42; p < 0.001), no prior shoulder surgery (OR, 1.79; 95% CI, 1.18-2.70; p = 0.006), humeral head not superiorly displaced on the AP radiograph (OR, 2.14; 95% CI, 1.15-4.02; p = 0.017), and glenoid type other than A1 (OR, 4.47; 95% CI, 2.24-8.94; p < 0.001). Neither preoperative glenoid version nor posterior decentering of the humeral head on the glenoid were associated with the outcomes. The model predictive of a better result was driven mainly by the six factors listed above. The area under the receiver operating characteristic curve generated from the cross-validated enhanced predictive model was 0.79 (generally values of 0.7 to 0.8 are considered fair and values of 0.8 to 0.9 are considered good). The false-positive fraction and the true-positive fraction depended on the cutoff probability selected (ie, the selected probability above which the prediction would be classified as a better outcome). A cutoff probability of 0.68 yielded the best performance of the model with cross-validation predictions of better outcomes for 236 patients (80%) and worse outcomes for 58 patients (20%); sensitivity of 91% (95% CI, 88%-95%); specificity of 65% (95% CI, 53%-77%); positive predictive value of 92% (95% CI, 88%-95%); and negative predictive value of 64% (95% CI, 51%-76%).

CONCLUSIONS

We found six easy-to-determine preoperative patient and shoulder factors that were significantly associated with better outcomes of shoulder arthroplasty. A model based on these characteristics had good predictive properties for identifying patients likely to have a better outcome from shoulder arthroplasty. Future research could refine this model with larger patient populations from multiple practices.

LEVEL OF EVIDENCE

Level II, therapeutic study.

Impaction autografting: bone-preserving, secure fixation of a standard humeral component

BACKGROUND

When fixed with bone ingrowth, a tight diaphyseal press fit, or cement, the humeral component of a shoulder arthroplasty may present problems of malposition, stress shielding, or periprosthetic fracture or difficulty with removal at revision arthroplasty. We have avoided the need for these fixation methods by using impaction cancellous autografting of the humeral stem, minimizing contact between the prosthetic stem and the humeral cortex. This study presents the radiographic survivorship of impaction-autografted humeral implants using component subsidence as the primary endpoint.

METHODS

We reviewed 286 primary anatomic shoulder arthroplasties having an average follow-up of 4.9 ± 2.7 years. Initial postoperative radiographs and minimum 2-year follow-up radiographs were evaluated by 3 observers to assess subsidence.

RESULTS

Two different implants (Humeral Replacement Prosthesis [HRP] and Global Advantage prosthesis) were used. Of 286 stems, 267 (93.4%) had not subsided. The Global Advantage prosthesis had a subsidence-free survival rate of 98.5% at 5 years. The stiffer-stemmed HRP used early during the study had a higher rate of subsidence compared with the currently used Global Advantage stem (hazard ratio, 5.6; P = .001). Radiolucent lines of 2 mm or greater were less common for the Global Advantage prosthesis than for the HRP in each of 7 zones (P < .001). Total shoulder arthroplasty was associated with a higher rate of subsidence compared with hemiarthroplasty (hazard ratio, 2.6; P = .12).

CONCLUSIONS

Impaction autografting provides a secure, durable, bone-preserving means of humeral component fixation in anatomic shoulder arthroplasty.

Likelihood-Based Inference of B Cell Clonal Families

The human immune system depends on a highly diverse collection of antibody-making B cells. B cell receptor sequence diversity is generated by a random recombination process called “rearrangement” forming progenitor B cells, then a Darwinian process of lineage diversification and selection called “affinity maturation.” The resulting receptors can be sequenced in high throughput for research and diagnostics. Such a collection of sequences contains a mixture of various lineages, each of which may be quite numerous, or may consist of only a single member. As a step to understanding the process and result of this diversification, one may wish to reconstruct lineage membership, i.e. to cluster sampled sequences according to which came from the same rearrangement events. We call this clustering problem “clonal family inference.” In this paper we describe and validate a likelihood-based framework for clonal family inference based on a multi-hidden Markov Model (multi-HMM) framework for B cell receptor sequences. We describe an agglomerative algorithm to find a maximum likelihood clustering, two approximate algorithms with various trade-offs of speed versus accuracy, and a third, fast algorithm for finding specific lineages. We show that under simulation these algorithms greatly improve upon existing clonal family inference methods, and that they also give significantly different clusters than previous methods when applied to two real data sets.

Antibodies must recognize a great diversity of antigens to protect us from infectious disease. The binding properties of antibodies are determined by the DNA sequences of their corresponding B cell receptors (BCRs). These BCR sequences are created in naive form by VDJ recombination, which randomly selects and trims the ends of V, D, and J genes, then joins the resulting segments together with additional random nucleotides. If they pass initial screening and bind an antigen, these sequences then undergo an evolutionary process of reproduction, mutation, and selection, revising the BCR to improve binding to its cognate antigen. It has recently become possible to determine the BCR sequences resulting from this process in high throughput. Although these sequences implicitly contain a wealth of information about both antigen exposure and the process by which we learn to resist pathogens, this information can only be extracted using computer algorithms. In this paper we describe a likelihood-based statistical method to determine, given a collection of BCR sequences, which of them are derived from the same recombination events. It is based on a hidden Markov model (HMM) of VDJ rearrangement which is able to calculate likelihoods for many sequences at once.

Loose glenoid components in revision shoulder arthroplasty: is there an association with positive cultures?

BACKGROUND

Glenoid loosening is one of the most common causes of total shoulder failure. High rates of positive cultures of Propionibacterium and coagulase-negative staphylococcus have been found among shoulders having surgical revision for glenoid loosening. This study reviewed the culture results in a series of surgical revisions for failed total shoulder arthroplasty to determine the relationship between glenoid loosening and positive cultures.

METHODS

The medical records of 221 patients without obvious evidence of infection who underwent revision total shoulder arthroplasty were reviewed to examine the association between the security of fixation of the glenoid component and the results of cultures obtained at revision surgery.

RESULTS

Of the revised shoulders, 53% had positive cultures; 153 of the shoulders (69%) had a loose glenoid component, whereas 68 (31%) had secure glenoid component fixation. Of the 153 loose glenoid components, 82 (54%) had at least 1 positive culture and 44 (29%) had 2 or more positive cultures of the same microorganism. Similarly, of the 68 secure glenoid components, 35 (51%) had at least 1 positive culture (P = .77) and 14 (21%) had 2 or more positive cultures of the same microorganism (P = .25). Explanted glenoid components that were loose had a higher rate of culture positivity (56% [24/43]) in comparison to explanted glenoid components that were well fixed (13% [1/8]) (P = .05).

CONCLUSION

Propionibacterium and coagulase-negative staphylococcus are commonly recovered in revision shoulder arthroplasty, whether or not the glenoid components are loose.

Quantifying evolutionary constraints on B-cell affinity maturation

The antibody repertoire of each individual is continuously updated by the evolutionary process of B-cell receptor (BCR) mutation and selection. It has recently become possible to gain detailed information concerning this process through high-throughput sequencing. Here, we develop modern statistical molecular evolution methods for the analysis of B-cell sequence data, and then apply them to a very deep short-read dataset of BCRs. We find that the substitution process is conserved across individuals but varies significantly across gene segments. We investigate selection on BCRs using a novel method that side-steps the difficulties encountered by previous work in differentiating between selection and motif-driven mutation; this is done through stochastic mapping and empirical Bayes estimators that compare the evolution of in-frame and out-of-frame rearrangements. We use this new method to derive a per-residue map of selection, which provides a more nuanced view of the constraints on framework and variable regions.

Propionibacterium in Shoulder Arthroplasty: What We Think We Know Today

➤ Propionibacterium is a slow-growing gram-positive rod that is part of the normal skin microbiome but can be found on culture of specimens from a large number of patients having revision shoulder arthroplasty performed for pain, stiffness, and component loosening. ➤ Propionibacterium infections do not present with obvious signs of infection, such as swelling, erythema, drainage, or tenderness, but rather are of the so-called stealth type, presenting with unexplained pain, stiffness, or component loosening months to years after the index arthroplasty. ➤ Not all propionibacteria are the same: certain subtypes of Propionibacterium are enriched with virulence factors that may enhance deep infection. ➤ Because propionibacteria typically reside in the pilosebaceous glands of the oily skin of the chest and back, standard surgical skin preparation solutions and even perioperative intravenous antibiotics are often inadequate at sterilizing the incision site; therefore, other prophylactic measures such as meticulous implant handling to avoid contact with dermal structures need to be considered. ➤ Recovery of Propionibacterium from the surgical wounds requires that multiple specimens for culture be taken from different areas of the shoulder to reduce sampling error, and cultures should be held for two weeks on multiple culture media. ➤ Future research efforts can be focused on reducing the risk of implant infection and point-of-care methods for identifying Propionibacterium infections.

Measurement of active shoulder motion using the Kinect, a commercially available infrared position detection system

BACKGROUND

The shoulder's ability to participate in sports and activities of daily living depends on its active range of motion. Clinical goniometry is of limited utility in rigorously assessing limitation of motion and the effectiveness of treatment. We sought to determine (1) whether a validated position-sensing tool, the Kinect, can enable the objective clinical measurement of shoulder motion and (2) the degree to which active range of motion correlates with patient self-assessed shoulder function.

METHODS

In 10 control subjects, we compared Kinect motion measurements to measurements made on standardized anteroposterior and lateral photographs taken concurrently. In 51 patients, we correlated active motion with the ability to perform the functions of the Simple Shoulder Test (SST).

RESULTS

In controls, Kinect measurements strongly agreed with photographic measurements. In patients, the total SST score was strongly correlated with the range of active abduction. The ability to perform each of the individual SST functions was strongly correlated with active motion. The active motion in well-functioning patient shoulders averaged 155° ± 22° abduction, 159° ± 14° flexion, 76° ± 18° external rotation in abduction, -59° ± 25° internal rotation in abduction, and -3.3 ± 3.7 inches of cross-body adduction, values similar to the control shoulders. Use of the Kinect system was practical in clinical examination rooms, requiring <5 minutes to document the 5 motions in both shoulders.

DISCUSSION

The Kinect provides a clinically practical method for objectively measuring active shoulder motion. Active motion was an important determinant of patient-assessed shoulder function.

Consistency of VDJ Rearrangement and Substitution Parameters Enables Accurate B Cell Receptor Sequence Annotation

VDJ rearrangement and somatic hypermutation work together to produce antibody-coding B cell receptor (BCR) sequences for a remarkable diversity of antigens. It is now possible to sequence these BCRs in high throughput; analysis of these sequences is bringing new insight into how antibodies develop, in particular for broadly-neutralizing antibodies against HIV and influenza. A fundamental step in such sequence analysis is to annotate each base as coming from a specific one of the V, D, or J genes, or from an N-addition (a.k.a. non-templated insertion). Previous work has used simple parametric distributions to model transitions from state to state in a hidden Markov model (HMM) of VDJ recombination, and assumed that mutations occur via the same process across sites. However, codon frame and other effects have been observed to violate these parametric assumptions for such coding sequences, suggesting that a non-parametric approach to modeling the recombination process could be useful. In our paper, we find that indeed large modern data sets suggest a model using parameter-rich per-allele categorical distributions for HMM transition probabilities and per-allele-per-position mutation probabilities, and that using such a model for inference leads to significantly improved results. We present an accurate and efficient BCR sequence annotation software package using a novel HMM "factorization" strategy. This package, called partis (https://github.com/psathyrella/partis/), is built on a new general-purpose HMM compiler that can perform efficient inference given a simple text description of an HMM.

The evolution within us

The B-cell immune response is a remarkable evolutionary system found in jawed vertebrates. B-cell receptors, the membrane-bound form of antibodies, are capable of evolving high affinity to almost any foreign protein. High germline diversity and rapid evolution upon encounter with antigen explain the general adaptability of B-cell populations, but the dynamics of repertoires are less well understood. These dynamics are scientifically and clinically important. After highlighting the remarkable characteristics of naive and experienced B-cell repertoires, especially biased usage of genes encoding the B-cell receptors, we contrast methods of sequence analysis and their attempts to explain patterns of B-cell evolution. These phylogenetic approaches are currently unlinked to explicit models of B-cell competition, which analyse repertoire evolution at the level of phenotype, the affinities and specificities to particular antigenic sites. The models, in turn, suggest how chance, infection history and other factors contribute to different patterns of immunodominance and protection between people. Challenges in rational vaccine design, specifically vaccines to induce broadly neutralizing antibodies to HIV, underscore critical gaps in our understanding of B cells' evolutionary and ecological dynamics.

How do revised shoulders that are culture positive for Propionibacterium differ from those that are not?

BACKGROUND

Many shoulder arthroplasties revised for pain, stiffness, or component loosening are culture positive for Propionibacterium. The culture results are unknown until days or weeks after surgery, too late to inform intraoperative surgical decisions and immediate postsurgical antibiotic treatment. The objective of this study was to identify preoperative and intraoperative characteristics that may alert surgeons to an increased likelihood of positive cultures.

METHODS

We analyzed the records of 132 shoulders that underwent surgical revision of a shoulder arthroplasty, 66 of which became culture positive for Propionibacterium and 66 did not.

RESULTS

Propionibacterium-positive and Propionibacterium-negative shoulders were similar with respect to many characteristics; however, Propionibacterium-negative shoulders were revised sooner after the index procedure and were significantly more likely to be female, to have sustained a fall, to have instability, and to have rotator cuff deficiency. Intraoperatively, Propionibacterium-positive shoulders demonstrated more glenoid erosions, glenoid osteolysis, glenoid loosening, and a higher incidence of a soft tissue membrane between the humeral component and humeral endosteum. Shoulders culture positive for Propionibacterium were more likely to be culture positive for another bacteria.

CONCLUSIONS

Although Propionibacterium-positive and Propionibacterium-negative shoulders have many similarities, factors such as male gender, delayed presentation, glenoid osteolysis and loosening, humeral membrane, and the absence of instability or cuff failure should arouse suspicion of Propionibacterium and suggest the need for deep cultures and consideration of aggressive surgical and medical treatment.

Factors Affecting Length of Stay, Readmission, and Revision After Shoulder Arthroplasty: A Population-Based Study

BACKGROUND

Increased length of hospital stay, hospital readmission, and revision surgery are adverse outcomes that increase the cost of elective orthopaedic procedures, such as shoulder arthroplasty. Awareness of the factors related to these adverse outcomes will help surgeons and medical centers design strategies for minimizing their occurrence and for managing their associated costs.

METHODS

We analyzed data from the New York Statewide Planning and Research Cooperative System on 17,311 primary shoulder arthroplasties performed from 1998 to 2011 to identify factors associated with extended lengths of hospitalization after surgery, readmission within ninety days, and surgical revision.

RESULTS

The factors associated with each of these three adverse outcomes were different. Longer lengths of hospital stay were associated with female sex, advanced patient age, Medicaid insurance, comorbidities, fracture as the diagnosis for arthroplasty, higher hospital case volumes, and lower surgeon case volumes. Readmission was associated with advanced patient age and medical comorbidities. The most common diagnoses for readmission within ninety days were fluid and electrolyte imbalance (28%), acute pulmonary problems (21%), cardiac arrhythmia (20%), heart failure (15%), acute myocardial infarction (10%), and urinary tract infection (10%). Revision was associated with younger patient age and osteoarthritis or traumatic arthritis. The most common diagnoses at the time of revision surgery were unspecified mechanical complications of the implant (60%), shoulder pain (18%), dislocation of the prosthetic joint (12%), component loosening (10%), a broken prosthesis (8%), a cuff tear (7%), and infection (7%).

CONCLUSIONS

A small number of easily identified characteristics (sex, age, race, insurance type, comorbidities, diagnosis, and provider case volumes) were significantly associated with longer lengths of stay, readmission, and revision surgery. Consideration of these factors and their effects may guide efforts to improve patient safety and to manage the costs associated with these adverse outcomes.

Bacterial Composition of the Human Upper Gastrointestinal Tract Microbiome Is Dynamic and Associated with Genomic Instability in a Barrett's Esophagus Cohort

Background

The incidence of esophageal adenocarcinoma (EAC) has increased nearly five-fold over the last four decades in the United States. Barrett’s esophagus, the replacement of the normal squamous epithelial lining with a mucus-secreting columnar epithelium, is the only known precursor to EAC. Like other parts of the gastrointestinal (GI) tract, the esophagus hosts a variety of bacteria and comparisons among published studies suggest bacterial communities in the stomach and esophagus differ. Chronic infection with Helicobacter pylori in the stomach has been inversely associated with development of EAC, but the mechanisms underlying this association remain unclear.

Methodology

The bacterial composition in the upper GI tract was characterized in a subset of participants (n=12) of the Seattle Barrett’s Esophagus Research cohort using broad-range 16S PCR and pyrosequencing of biopsy and brush samples collected from squamous esophagus, Barrett’s esophagus, stomach corpus and stomach antrum. Three of the individuals were sampled at two separate time points. Prevalence of H. pylori infection and subsequent development of aneuploidy (n=339) and EAC (n=433) was examined in a larger subset of this cohort.

Results/Significance

Within individuals, bacterial communities of the stomach and esophagus showed overlapping community membership. Despite closer proximity, the stomach antrum and corpus communities were less similar than the antrum and esophageal samples. Re-sampling of study participants revealed similar upper GI community membership in two of three cases. In this Barrett’s esophagus cohort, Streptococcus and Prevotella species dominate the upper GI and the ratio of these two species is associated with waist-to-hip ratio and hiatal hernia length, two known EAC risk factors in Barrett’s esophagus. H. pylori-positive individuals had a significantly decreased incidence of aneuploidy and a non-significant trend toward lower incidence of EAC.

Can the ream and run procedure improve glenohumeral relationships and function for shoulders with the arthritic triad?

BACKGROUND

The arthritic triad of glenoid biconcavity, glenoid retroversion, and posterior displacement of the humeral head on the glenoid is associated with an increased risk of failure of total shoulder joint replacement. Although a number of glenohumeral arthroplasty techniques are being used to manage this complex pathology, problems with glenoid component failure remain. In that the ream and run procedure manages arthritic pathoanatomy without a glenoid component, we sought evidence that this procedure can be effective in improving the centering of the humeral head contact on the glenoid and in improving the comfort and function of shoulders with the arthritic triad without the risk of glenoid component failure.

QUESTIONS/PURPOSES

We asked, for shoulders with the arthritic triad, whether the ream and run procedure could improve glenohumeral relationships as measured on standardized axillary radiographs and patient-reported shoulder comfort and function as recorded by the Simple Shoulder Test.

METHODS

Between January 1, 2006 and December 14, 2011, we performed 531 primary anatomic glenohumeral arthroplasties for arthritis, of which 221 (42%) were ream and run procedures. Of these, 30 shoulders in 30 patients had the ream and run procedure for the arthritic triad and had two years of clinical and radiographic follow-up. These 30 shoulders formed the basis for this case series. The average age of the patients was 56 ± 8 years; all but one were male. Two of the 30 patients requested revision to total shoulder arthroplasty within the first year after their ream and run procedure because of their dissatisfaction with their rehabilitation progress. For the 28 shoulders not having had a revision, we determined on the standardized axillary views before and after surgery the glenoid type, glenoid version (90° minus the angle between the plane of the glenoid face and the plane of the body of the scapula), and location of the humeral contact point with respect to the anteroposterio dimension of the glenoid (the ratio of the distance from the anterior glenoid lip to the contact point divided by the distance between the anterior and posterior glenoid lips). We also recorded the patient's self-assessed shoulder comfort and function before and after surgery using the 12 questions of the Simple Shoulder Test.

RESULTS

For the 28 unrevised shoulders the mean followup was 3.0 years (range, 2-9.2 years). In these patients, the ream and run procedure resulted in improved centering of the humeral head on the face of the glenoid (preoperative: 75% ± 7% posterior; postoperative: 59% ± 10% posterior; mean difference 16% [95% CI, 13%-19%]; p < 0.001), notably this improved centering was achieved without a significant change in the glenoid version. Patient-reported function was improved (preoperative Simple Shoulder Test: 5 ± 3, postoperative Simple Shoulder Test: 10 ± 4, mean difference 5 [95% CI, 4-6], p < 0.001).

CONCLUSIONS

For shoulders with the arthritic triad, the ream and run procedure can provide improvement in humeral centering on the glenoid and in patient-reported shoulder comfort and function without the risk of glenoid component failure. In that ream and run is a new procedure, substantial additional clinical research with long-term follow-up is needed to define specifically the shoulder characteristics, the patient characteristics and the technical details that are most likely to lead to durable improvements in the comfort and function of shoulders with the challenging pathology known as the arthritic triad.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Rotator cuff repair: published evidence on factors associated with repair integrity and clinical outcome

BACKGROUND

Rotator cuff tears are common, and rotator cuff repair represents a major health care expense. While patients often benefit from rotator cuff repair, anatomic failure of the repair is not unusual.

PURPOSE

To identify the published evidence on the factors associated with retears and with suboptimal clinical outcomes of rotator cuff repairs.

STUDY DESIGN

Systematic review and meta-analysis of articles with evidence levels 1-4.

METHODS

A total of 2383 articles on rotator cuff repairs published between 1980 and 2012 were identified. Only 108 of these articles, reporting on over 8011 shoulders, met the inclusion criteria of reporting quantitative data on both imaging and clinical outcomes after rotator cuff repair. Factors related to the patients, their shoulders, the procedures, and the results were systematically categorized and submitted for meta-analysis.

RESULTS

While the number of relevant articles published per year increased dramatically over the period of the study, the clinical and anatomic results did not show improvement over this period. The weighted mean retear rate was 26.6% at a mean of 23.7 months after surgery. Retears were associated with more fatty infiltration, larger tear size, advanced age, and double-row repairs. Clinical improvement averaged 72% of the maximum possible improvement. Patient-reported outcomes were generally improved whether or not the repair restored the integrity of the rotator cuff. The inconsistent and incomplete data in the published articles limited the meta-analysis of factors affecting the outcome of rotator cuff repair.

CONCLUSION

In spite of a dramatic increase in the number of publications per year, there is little evidence that the results of rotator cuff repair are improving. The information needed to guide the management of this commonly treated and costly condition is seriously deficient. To accumulate the evidence necessary to inform practice, future clinical studies on the outcome of rotator cuff repair must report important data relating to each patient's condition, the surgical technique, the outcome in terms of integrity, and the change in patient self-assessed comfort and function.