Relative fixation strength of rabbit subscapularis repair is comparable to human supraspinatus repair at time 0.

BACKGROUND: Recent evidence suggests that the rabbit subscapularis tendon may be anatomically, biomechanically, and histologically suitable to study rotator cuff pathology and repair. However, biomechanical comparisons of rotator cuff repairs in this model have not been evaluated and compared to those in human cadaveric specimens. QUESTIONS/PURPOSES: We quantified the biomechanical properties of the repaired rabbit subscapularis tendon after (1) single-row, (2) double-row, and (3) transosseous-equivalent rotator cuff repair techniques and compared the ratios of repairs to previously published data for human repairs. METHODS: Tensile testing was performed on 21 New Zealand White rabbit subscapularis tendon-humerus complexes for single-row repair, double-row repair, and transosseous-equivalent repair (n = 7 for each group). Video digitizing software was used to quantify deformation. Load elongation data were then used to quantify structural properties. We compared the ratios of rotator cuff repairs for the rabbit data to data from human supraspinatus repair studies previously performed in our laboratory. For our primary end points (linear stiffness, yield load, ultimate load, and energy absorbed to failure), with the numbers available, our statistical power to detect a clinically important difference (defined as 15%) was 85%. RESULTS: The ratios of single-row/double-row repair were 0.72, 0.73, 0.71, and 0.66 for human supraspinatus and 0.77, 0.74, 0.79, and 0.89 for rabbit subscapularis repair for linear stiffness, yield load, ultimate load, and energy absorbed to failure, respectively. The ratios of double-row/transosseous-equivalent repair were 1.0, 0.86, 0.70, and 0.41 for human supraspinatus and 1.22, 0.85, 0.76, and 0.60 for rabbit subscapularis for linear stiffness, yield load, ultimate load, and energy absorbed to failure, respectively. There were no differences comparing rabbit to human repair ratios for any parameter (p > 0.09 for all comparisons). CONCLUSIONS: Subscapularis repairs in the rabbit at Time 0 result in comparable ratios to human supraspinatus repairs. CLINICAL RELEVANCE: The biomechanical similarities between the different types of rotator cuff repair in the rabbit subscapularis and human supraspinatus at Time 0 provide more evidence that the rabbit subscapularis may be an appropriate model to study rotator cuff repairs.

Fixation of periprosthetic femoral shaft fractures associated with cemented femoral stems: a biomechanical comparison of locked plating and conventional cable plates.

UNLABELLED: To determine which of 2 techniques for the treatment of periprosthetic femoral shaft fractures is of greater stiffness. DESIGN: A laboratory study using 8 pairs of matched, embalmed femurs. METHODS: Femurs implanted with a cemented total hip prosthesis had a simulated periprosthetic femur fracture created distal to the implant. Fractures were fixed with a plate with locked screws or a plate with cables (Ogden construct). Fixation stability was compared in various loading modalities before and after cycling. Failure in torsional loading was then determined. The cement mantle was tested for crack propagation that may have occurred secondary to locked screw insertion and loading. OUTCOME MEASUREMENTS: Fixation stiffness (the ratio of applied load to displacement at the fracture site), torsional strength, mode of failure for each system, and cement mantle evaluation for cracks after screw insertion. RESULTS: Locked plating was stiffer than the Ogden construct in pre- and post-cyclic axial loading and torsion. There was no difference in lateral bending stability or torsional failure loads. CONCLUSIONS: Locked plating constructs were stiffer than the Ogden construct in axial loading and torsion. Although no differences in loads to failure during torsion were noted, locked plating constructs exhibited catastrophic failure not observed with the Ogden construct.

The consistency between scientific papers presented at the Orthopaedic Trauma Association and their subsequent full-text publication.

OBJECTIVES: To determine the consistency of conclusions/statements made in podium presentations at the annual meeting of the Orthopaedic Trauma Association (OTA) with those in subsequent full-text publications. Also, to evaluate the nature and consistency of study design, methods, sample sizes, results and assign a corresponding level of evidence. DATA SOURCES: Abstracts of the scientific programs of the OTA from 1994 to 1997 (N = 254) were queried by using the PubMed database to identify those studies resulting in a peer-reviewed, full-text publication. STUDY SELECTION: Of the 169 articles retrieved, 137 studies were the basis of our study after the exclusion criteria were applied: non-English language, basic science studies, anatomic dissection studies, and articles published in non-peer-reviewed journals. DATA EXTRACTION/SYNTHESIS: Information was abstracted onto a data form: first from the abstract published in the final meeting program, and then from the published journal article. Information was recorded regarding study issues, including the study design, primary objective, sample size, and statistical methods. We provided descriptive statistics about the frequency of consistent results between abstracts and full-text publications. The results were recorded as percentages and a 95% confidence interval was applied to each value. Study results were recorded for the abstract and full-text publication comparing results and the overall conclusion. A level of scientific-based evidence was assigned to each full-text publication. RESULTS: The final conclusion of the study remained the same 93.4% of the time. The method of study was an observational case series 52% of the time and a statement regarding the rate of patient follow-up was reported 42% of the time. Of the studies published, 18.2% consisted of a sample size smaller than the previously presented abstract. When the published papers had their level of evidence graded, 11% were level I, 16% level II, 17% level III, and 56% level IV. CONCLUSIONS: Authors conclusions were consistent with those in full-text publications. Most studies were observational, less than half reported on the rate of patient follow-up. Many abstracts followed by publication had a smaller sample size in the published paper. Half of all studies were graded level IV evidence.

Serum interleukin-6 as a marker of periprosthetic infection following total hip and knee arthroplasty.

BACKGROUND: The erythrocyte sedimentation rate, the C-reactive protein serum level, and the white blood-cell count are routinely used to diagnose periprosthetic infection. In the present study, the diagnostic accuracy of the interleukin-6 serum level was compared with the accuracy of these standard tests for the evaluation of a group of patients who had had a total hip or total knee arthroplasty and were undergoing a reoperation for the treatment of an infection or another implant-related problem. METHODS: A prospective, case-control study of fifty-eight patients who had had a total hip or knee replacement and were undergoing a reoperation because of an infection (seventeen patients) or another implant-related problem (forty-one patients) was conducted. The serum levels of interleukin-6 and C-reactive protein, the erythrocyte sedimentation rate, and the white blood-cell count were measured. The definitive diagnosis of an infection was determined on the basis of positive histopathological evidence of infection and growth of bacteria on culture of intraoperative specimens. Two-sample Wilcoxon rank-sum (Mann-Whitney) tests were used to determine the presence of a significant difference between patients with and without infection with regard to each laboratory value studied. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of each text were also calculated. RESULTS: The serum interleukin-6 level, erythrocyte sedimentation rate, and C-reactive protein level were significantly higher in patients who had an infection than in those who did not, both when all patients were considered together and when the total hip arthroplasty and total knee arthroplasty groups were considered separately. With the numbers available, there was no significant difference with regard to the white blood-cell count between patients with and without infection. With a normal serum interleukin-6 level defined as <10 pg/mL, the serum interleukin-6 test had a sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 1.0, 0.95, 0.89, 1.0, and 97%, respectively. CONCLUSIONS: An elevated serum interleukin-6 level correlated positively with the presence of periprosthetic infection in patients undergoing a reoperation at the site of a total hip or knee arthroplasty. The serum interleukin-6 level is valuable for the diagnosis of periprosthetic infection in patients who have had a total hip or total knee arthroplasty.

Osteotomy about the knee: applications, techniques, and results.

Varus or valgus malalignment of the knee may be either a cause or a consequence of unicompartmental knee arthritis in young, active adults. Proximal tibial osteotomy for the varus knee and distal femoral osteotomy for the valgus knee have been used for decades to manage this condition; however, their use has decreased significantly in recent years as the popularity of unicompartmental and total knee arthroplasty has grown. With the advent of biologic resurfacing techniques for focal full-thickness articular cartilage injury, combined or staged high tibial osteotomy is becoming increasingly popular. In addition, in the face of cruciate ligamentous instability with or without posterolateral corner instability coupled with varus malalignment, high tibial osteotomy with and without ligament reconstruction provides a solution to complex orthopedic problems. Recent long-term follow-up studies have concluded osteotomy allows for improved function and pain relief in properly selected young patients.

Midshaft clavicle fractures in adults.

Clavicle fractures remain one of the more common fractures encountered in the orthopaedic office. Nonoperative management remains the standard of care in most cases. However, studies have shown a higher nonunion rate and decreased patient satisfaction in fractures with increased shortening. The malunion resulting from nonoperative management has been shown to be problematic in patients with significant fracture shortening. When operative reduction and fixation is indicated, there are numerous techniques to aid the surgeon patient care. This article reviews the midshaft clavicle fracture and discusses recent outcome studies on patients with fracture shortening and approaches to operative management.

Podium versus poster publication rates at the Orthopaedic Trauma Association.

Original studies at orthopaedic meetings are presented on the podium and in poster format. Publication of those studies in peer-reviewed journals is the standard of communicating scientific data to colleagues. Investigators of previous studies have reported publication rates, but never differentiated between the modes of presentation. We evaluated the annual meeting of the Orthopaedic Trauma Association from 1994-1998 and found that studies presented on the podium were 1.3 times more likely to be published than those presented in a poster format (67% versus 52%). The mean time to publication was similar, 21.6 months for poster presentations and 24.8 months for podium presentations. Podium presentations were more likely to be published in the Journal of Orthopaedic Trauma, Clinical Orthopaedics and Related Research, and the Journal of Bone and Joint Surgery (American and British editions). Our findings suggest different rates and distribution of publication between podium and poster presentations at an international trauma meeting. These findings should be considered when evaluating studies of interest at the Orthopaedic Trauma Association meeting.

tipE regulates Na+-dependent repetitive firing in Drosophila neurons.

The tipE gene, originally identified by a temperature-sensitive paralytic mutation in Drosophila, encodes a transmembrane protein that dramatically influences sodium channel expression in Xenopus oocytes. There is evidence that tipE also modulates sodium channel expression in the fly; however, its role in regulating neuronal excitability remains unclear. Here we report that the majority of neurons in both wild-type and tipE mutant (tipE-) embryo cultures fire sodium-dependent action potentials in response to depolarizing current injection. However, the percentage of tipE- neurons capable of firing repetitively during a sustained depolarization is significantly reduced. Expression of a tipE+ transgene, in tipE- neurons, restores repetitive firing to wild-type levels. Analysis of underlying currents reveals a slower rate of repolarization-dependent recovery of voltage-gated sodium currents during repeated activation in tipE- neurons. This phenotype is also rescued by expression of the tipE+ transgene. These data demonstrate that tipE regulates sodium-dependent repetitive firing and recovery of sodium currents during repeated activation. Furthermore, the duration of the interstimulus interval necessary to fire a second full-sized action potential is significantly longer in single- versus multiple-spiking transgenic neurons, suggesting that a slow rate of recovery of sodium currents contributes to the decrease in repetitive firing in tipE- neurons.