Effect of surgeon fatigue on hip and knee arthroplasty.

BACKGROUND: There is growing support in the literature that patient outcomes are adversely affected by physician fatigue in operator-dependent cognitive and technical tasks. Recent increases in total joint arthroplasty caseloads have resulted in longer operative days and increased surgeon fatigue. We sought to determine if time of day predicts perioperative complications and outcomes in total joint arthroplasty. METHODS: The records of all total hip and knee arthroplasties (THA; TKA) performed for primary osteoarthritis in one calendar year at one large university hospital were retrospectively reviewed. Demographic data, surgery start time and duration, intraoperative complications, radiographic component alignment and functional outcome scores (SF-12 and Western Ontario and McMaster Universities Osteoarthritis Index) were collected and analyzed using linear and nonparametric rank correlation statistics. Data were corrected for sex, body mass index, surgeon and postcall operating days. RESULTS: In the THA cohort (n=341), a later surgery start time was significantly related to duration of surgery (p= 0.004, mean difference -7.1 min). There was a trend toward significance between a later surgery start time and intraoperative femur fracture (p= 0.05). Postoperative complications, component alignment and functional outcome scores were not significantly affected by surgery start time. There were no significant findings for any of the intraoperative or postoperative outcomes in the TKA cohort (n=292). CONCLUSION: Duration of surgery and incidence of intraoperative complications for THA may increase with later surgery start time; however, the relatively small statistical differences observed imply that they likely are not clinically significant.

Treatment of periprosthetic fractures around hip resurfacings with cephalomedullary nails.

We describe 2 cases of proximal femoral fractures, 1 intertrochanteric and 1 subtrochanteric, distal to hip resurfacing implants that were managed successfully via internal fixation with trochanteric start point cephalomedullary nails. Both patients had pain-free, well-functioning implants with radiographically healed fractures at their 1-year follow-up. This novel approach offers several advantages over previously described techniques for these rare and difficult-to-treat fractures.

Risk factors for peroneal nerve injury and recovery in knee dislocation.

BACKGROUND: Acute knee dislocation is rare but has a high rate of associated neurovascular injuries and potentially limb-threatening complications. These include the substantial morbidity associated with peroneal nerve injury: neuropathic pain, decreased mobility, and considerably reduced function, which not only impairs patient function but complicates treatment. QUESTIONS/PURPOSES: We therefore identified and quantified the risks associated with specific factors for peroneal nerve injury and recovery in patients with knee dislocations. PATIENTS AND METHODS: We retrospectively reviewed the charts of 26 patients, from among a cohort of all 91 knee dislocations, with a peroneal nerve palsy over a 5-year period. We then used univariable and multivariable statistics to identify risk factors predicting peroneal nerve injury and recovery. RESULTS: Gender (odds ratio, 5.47), body mass index (odds ratio, 1.14), and fibular head fracture (odds ratio, 4.77) were associated with peroneal nerve injury. Only younger age was associated with peroneal nerve recovery. CONCLUSIONS: Knowledge of the risk factors for peroneal nerve injury and the predictors of recovery in knee dislocation allows the treating surgeon to have a better understanding of the nature of the neurologic injury and modify management based on the anticipated return of nerve function. LEVEL OF EVIDENCE: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Cardiovascular disease predicts complications following bilateral total knee arthroplasty under a single anesthetic.

INTRODUCTION: This study evaluated the rate of perioperative complications of single anesthetic bilateral total knee arthroplasties (TKA) compared with staged procedures. METHODS: The records of all single anesthetic bilateral TKA performed between 1997 and 2007 at one large community hospital and one university hospital were retrospectively reviewed. Complete demographic data, preoperative co-morbidities and complications for 156 patients were compared to a matched staged bilateral TKA (n=78) cohort. RESULTS: In the single anesthetic bilateral TKA cohort, cardiovascular disease predicted postoperative myocardial (p<0.01, Odds Ratio - 67.6), need for ICU admission (p<0.01, Odds Ratio - 88.8), and days spent in ICU (p<0.01), while cardiovascular disease did not significantly predict postoperative MI in the staged bilateral (p=0.99, OR - 0). CONCLUSION: Patients with cardiovascular disease are at higher risk for perioperative MI after single anesthetic bilateral TKA.

Outcomes of operative and nonoperative treatment of multiligament knee injuries: an evidence-based review.

Knee dislocation is an uncommon orthopedic diagnosis with a high rate of neurovascular complications. The goal of definitive management is to provide a pain free and functional knee through restoration of ligamentous stability and range of motion. Operative management has been suggested to be superior to nonoperative management for knee dislocations largely in part owing to a meta-analysis on the topic published a decade ago. The purpose of this study was to summarize the results of operative and nonoperative treatment of knee dislocations over the past 10 year period. There were a total of 855 patients from 31 studies managed operatively and 61 patients from 4 studies managed nonoperatively. The overall methodological quality of the studies was poor as measured by the Newstead-Ottawa scale. Data regarding functional outcome, instability, contracture, and return to activity were all in favor of operative management. Significant differences were found for return to employment (P<0.001) and return to sport (P=0.001). The results of this study provide further evidence for the superiority of operative management, compared with nonoperative management, for knee dislocations across several clinical and functional domains. There is a need for higher level studies to assist the treating surgeon in the management of these challenging injuries.

Biomechanical measurements of torsion-tension coupling in human cadaveric femurs.

The mechanical behavior of human femurs has been described in the literature with regard to torsion and tension but only as independent measurements. However, in this study, human femurs were subjected to torsion to determine if a simultaneous axial tensile load was generated. Fresh frozen human femurs (n=25) were harvested and stripped of soft tissue. Each femur was mounted rigidly in a specially designed test jig and remained at a fixed axial length during all experiments. Femurs were subjected to external and internal rotation applied at a constant angulation rate of 0.1 deg/s to a maximum torque of 12 N m. Applied torque and generated axial tension were monitored simultaneously. Outcome measurements were extracted from torsion-versus-tension graphs. There was a strong relationship between applied torsion and the resulting tension for external rotation tests (torsion/tension ratio=551.7±283.8 mm, R(2)=0.83±0.20, n=25), internal rotation tests (torsion/tension ratio=495.3±233.1 mm, R(2)=0.87±0.17, n=24), left femurs (torsion/tension ratio=542.2±262.4 mm, R(2)=0.88±0.13, n=24), and right femurs (torsion/tension ratio=506.7±260.0 mm, R(2)=0.82±0.22, n=25). No statistically significant differences were found for external versus internal rotation groups or for left versus right femurs when comparing torsion/tension ratios (p=0.85) or R(2) values (p=0.54). A strongly coupled linear relationship between torsion and tension for human femurs was exhibited. This suggests an interplay between these two factors during activities of daily living and injury processes.

Diagnosis and management of knee dislocations.

An acute knee dislocation is an uncommon injury, with a high rate of associated vascular and neurologic injuries as well as potentially limb-threatening complications. High-energy trauma is the most common cause of an acute knee dislocation, although lower-energy injuries, such as those sustained during athletic competition, are increasing in incidence. Injuries to the popliteal artery and common peroneal nerve are relatively common, requiring a high index of suspicion and complete neurovascular examination in a timely fashion. All cases of suspected knee dislocation should have an ankle-brachial index performed, reserving arteriography for those with an abnormal finding. Initial management consists of closed reduction, if possible, and application of a hinged brace or external fixator. Definitive management remains an area of controversy, although anatomic surgical repair or reconstruction is favored by most surgeons to help optimize knee function. Most patients treated for a knee dislocation can expect to return to their daily activities, but with less predictable returns to sporting activities.

The biomechanics of ipsilateral intertrochanteric and femoral shaft fractures: a comparison of 5 fracture fixation techniques.

OBJECTIVES: The aim of the present study was to examine biomechanically 5 different construct combinations for fixation of ipsilateral intertrochanteric and femoral shaft fractures. METHODS: Twenty-five fresh-frozen adult human femora (age range = 58-91 years, average age = 75.4 years) were tested in physiological bending and in torsion to characterize initial bending and torsional stiffness and stiffness following fixation of combined intertrochanteric and femoral shaft fractures. Five fracture fixation device constructs were assessed-construct A: long dynamic hip screw (long DHS); construct B: reconstruction nail; construct C: DHS plus low-contact dynamic compression plate; construct D: DHS plus retrograde intramedullary nail; and construct E: long intramedullary hip screw. Axial stiffness, torsional stiffness, and axial load-to-failure were the main measurements recorded. RESULTS: There were no differences between constructs in terms of axial stiffness (P = 0.41), external rotation stiffness (P = 0.13), and axial load-to-failure (P = 0.16). However, there was a borderline statistically significant difference in internal rotation stiffness between the constructs (P = 0.048). Specifically, construct C was significantly stiffer than construct E (P = 0.04). CONCLUSIONS: All constructs showed no statistical differences when compared with one another, with the exception of construct E, which provided the least torsional stiffness. However, the current in vitro model did not simulate fracture healing or support offered by soft tissues, both of which would affect the stiffness and load-to-failure levels reached.

Functional outcome of ipsilateral intertrochanteric and femoral shaft fractures.

OBJECTIVES: The purpose of this study was to compare the functional outcome of patients with ipsilateral intertrochanteric and femoral shaft fractures treated with a reconstruction nail versus a sliding hip screw and retrograde nail. DESIGN: Retrospective cohort study. SETTING: Two level 1 trauma centers. PARTICIPANTS: Twenty-six patients with ipsilateral intertrochanteric and femoral shaft fractures treated between 1993 and 2003 with a reconstruction nail (n=13) or with a sliding hip screw and retrograde nail (n=13). INTERVENTION: Internal fixation with a reconstruction nail or a sliding hip screw and retrograde nail. MAIN OUTCOME MEASUREMENTS: Functional outcome was measured using the Short Form-36 (SF-36), Short Musculoskeletal Functional Assessment (SMFA), and Lower Extremity Functional Scale (LEFS). RESULTS: The average time to follow-up was 49.6 months. Functional outcome was significantly better in the sliding hip screw with retrograde nail group for the role emotional (P=0.001) and mental component scores (P=0.016) of the SF-36. This group also scored better on the LEFS, although not reaching statistical significance (P=0.099). CONCLUSIONS: For most outcome measures, no significant differences in functional outcome scores were observed between the 2 treatment groups. The results of this study suggest the need for a randomized controlled trial with a larger sample size to more definitively compare the 2 fixation constructs.

Effectiveness of medical school admissions criteria in predicting residency ranking four years later.

BACKGROUND: Medical schools across Canada expend great effort in selecting students from a large pool of qualified applicants. Non-cognitive assessments are conducted by most schools in an effort to ensure that medical students have the personal characteristics of importance in the practice of Medicine. We reviewed the ability of University of Toronto academic and non-academic admission assessments to predict ranking by Internal Medicine and Family Medicine residency programmes. METHODS: The study sample consisted of students who had entered the University of Toronto between 1994 and 1998 inclusive, and had then applied through the Canadian resident matching programme to positions in Family or Internal Medicine at the University of Toronto in their graduating year. The value of admissions variables in predicting medical school performance and residency ranking was assessed. RESULTS: Ranking in Internal Medicine correlated significantly with undergraduate grade point average (GPA) and the admissions non-cognitive assessment. It also correlated with 2-year objective structured clinical examination (OSCE) score, clerkship grade in Internal Medicine, and final grade in medical school. Ranking in Family Medicine correlated with the admissions interview score. It also correlated with 2nd-year OSCE score, clerkship grade in Family Medicine, clerkship ward evaluation in Internal Medicine and final grade in medical school. DISCUSSION: The results of this study suggest that cognitive as well as non-cognitive factors evaluated during medical school admission are important in predicting future success in Medicine. The non-cognitive assessment provides additional value to standard academic criteria in predicting ranking by 2 residency programmes, and justifies its use as part of the admissions process.

Critical delay for overshooting in planned arm movements with delayed feedback.

The Vector Integration To Endpoint (VITE) circuit describes a real time neural network model which simulates behavioral and neurobiological properties of planned arm movements by the interaction of two populations of neurons. This model is generalized to include delay between the interacting populations, which is found to have a detrimental effect on movement accuracy. Conditions are given on the model parameters for accurate movement and target overshoot, where we show that there exists a non-zero critical value of the delay which the circuit can support while maintaining accurate movement. This critical delay depends on the movement speed, and becomes arbitrarily large for sufficiently slow movement. Thus neurobiological or artificial systems modelled by the VITE sensory-motor loop can tolerate an arbitrarily large delay if the movement speed is sufficiently slow.