Surgical Techniques for Total Knee Arthroplasty: Measured Resection, Gap Balancing, and Hybrid.

Total knee arthroplasty (TKA) is effective in managing end-stage degenerative joint disease. Achieving favorable clinical outcomes is predicated on proper implant alignment, sizing, and rotation as well as adequate soft-tissue balancing. Modern TKA implants are designed to address the fundamental needs of attaining stability in both flexion and extension and of optimizing patellar tracking. Measured resection and gap balancing are the two different techniques used to implant the TKA components used today. Both techniques have been validated as durable and successful, and each has unique advantages and disadvantages. A hybrid technique has been developed that combines the benefits of measured resection and gap balancing and minimizes the limitations associated with both techniques. This hybrid approach has the potential for achieving improved TKA kinematics and refined surgical technique.

Single-component revisions are associated with dislocation after revision total hip arthroplasty at intermediate-term follow-up.

PURPOSE: Dislocation is the most frequent complication following revision total hip arthroplasty (THA). Although several risk factors for dislocation in revision THA have been described, many cannot be modified at the time of surgery. Identifying modifiable risk factors for subsequent dislocation after revision THA provides opportunity for orthopedic surgeons to decrease instability. METHODS: A retrospective analysis of 203 consecutive revision THA procedures performed by a single surgeon with a minimum 2-year follow-up between May 2003 and June 2012 was performed. 2 (1.0%) died and 14 (6.9%) were lost to follow-up leaving 187 (92%) revision procedures in 123 men and 64 women. Univariate and multivariate logistic regression was used to identify risk factors for dislocation. RESULTS: 9 (4.8%) of all patients reviewed experienced a dislocation episode. Of those, 8 (89%) had a single component revised, 6 (67%) were women, and 4 (44%) had a history of recurrent dislocation. 2 of 14 (14%) patients with a constrained liner dislocated. Univariate analysis demonstrated that single-component revisions were at higher risk for dislocation after the surgery (p value = 0.033). CONCLUSIONS: Identifying modifiable risk factors for dislocation after revision THA provide opportunity to decrease rates of instability. Based on our data, single-component revision THA is a risk factor for subsequent dislocation.

A comparison of open versus percutaneous cervical transfacet fixation.

OBJECTIVE The aim of this study is to describe a technique for percutaneous cervical transfacet screw placement and compare this technique to the open technique with regard to the accuracy of facet capture and the potential of placing neurovascular structures at risk. METHODS Eight cadaveric cervical spines were harvested. One side of each spine was assigned to the percutaneous group, and the other side to the open group. The spines were instrumented from C-3 to T-1 (80 screws). The distance to the spinal canal, foramen transversarium, and neural foramen were measured to determine the likelihood of placing neurovascular structures at risk. The percentage of the facet joint captured and the angle of screw trajectory compared with the ideal trajectory were used to determine the accuracy. RESULTS There were, in total, 11 misplacements of screws: 2 screws using the open technique and 9 screws using the percutaneous technique (p = 0.006). From a neurovascular point of view, 3 percutaneous screws violated the foramen transversarium. Two of these percutaneous screws violated the neural foramen. No neurovascular foramina were violated using the open technique. The open technique resulted in a significantly greater distance from the screw to the spinal canal (p < 0.001). The distance from the screw to the foramen transversarium (p = 0.015), as well as the distance from the screw to the neural foramen (p = 0.012), did not demonstrate statistical difference when using either technique. As for the accuracy of facet capture, 8 screws exhibited less than 15% purchase of the facet joint. Six of these screws were placed using the percutaneous technique, and 2 screws were placed using the open technique. CONCLUSIONS There is a higher incidence of screw misplacement using the percutaneous transfacet in comparison to the open transfacet technique. The accuracies of facet capture using the 2 techniques were not statistically different. Surgeons will need to understand the potential risk of using the percutaneous technique as an alternative to open transfacet fixation.

Establishing Realistic Patient Expectations Following Total Knee Arthroplasty.

Nearly 20% of patients are dissatisfied following well-performed total knee arthroplasty with good functional outcomes. Surgeons must understand the drivers of dissatisfaction to minimize the number of unhappy patients following surgery. Several studies have shown that unfulfilled expectations are a principal source of patient dissatisfaction. Patients contemplating total knee arthroplasty expect pain relief, improved walking ability, return to sports, and improvement in psychological well-being and social interactions. However, patients are typically overly optimistic with regard to expected outcomes following surgery. Patient expectations and satisfaction can be influenced by age, socioeconomic factors, sex, and race. The interplay of these factors can be complex and specific to each person. Published data on clinical and functional outcomes show that persistence of symptoms, such as pain, stiffness, and failure to return to preoperative levels of function, are common and normal. Therefore, the surgeon needs to help the patient to establish realistic expectations.

Mini-external fixation of two- and three-part proximal humerus fractures.

A retrospective review of 64 patients (M 36, F 28, average age 55 years) with 29 two-part fractures and 35 three-part fractures of the proximal humerus was conducted at a Level 1 Trauma Center. All fractures were managed with the mini external fixator. Open reduction was performed in 11 cases, closed reduction in 53. The average follow-up was 21 months (range, 12-39). The final outcome, evaluated according to Neer's scoring system, was excellent in 63.4% of patients, good in 18.8%, fair in 12.7%, and poor in 5.1%. By 9 weeks, 85% of the fractures were healed and 97% by 12 weeks. Complications included nonunion, superficial infection and deep infection, in two cases for each. Bicipital tendonitis occurred in five cases and secondary displacement of the fragments in four others. The small diameter of the pins used in the mini external fixator has the advantage of allowing the orthopaedic surgeon to fix the fracture in more than one plane and achieve an early acceptable range of motion. This technique appears attractive especially in polytrauma patients, as the procedure can be performed in the supine position and causes no additional blood loss.

Effect of area x-ray beam equalization on image quality and dose in digital mammography.

In mammography, thick or dense breast regions persistently suffer from reduced contrast-to-noise ratio (CNR) because of degraded contrast from large scatter intensities and relatively high noise. Area x-ray beam equalization can improve image quality by increasing the x-ray exposure to under-penetrated regions without increasing the exposure to other breast regions. Optimal equalization parameters with respect to image quality and patient dose were determined through computer simulations and validated with experimental observations on a step phantom and an anthropomorphic breast phantom. Three parameters important in equalization digital mammography were considered: attenuator material (Z = 13-92), beam energy (22-34 kVp) and equalization level. A Mo/Mo digital mammography system was used for image acquisition. A prototype 16 x 16 piston driven equalization system was used for preparing patient-specific equalization masks. Simulation studies showed that a molybdenum attenuator and an equalization level of 20 were optimal for improving contrast, CNR and figure of merit (FOM = CNR2/dose). Experimental measurements using these parameters showed significant improvements in contrast, CNR and FOM. Moreover, equalized images of a breast phantom showed improved image quality. These results indicate that area beam equalization can improve image quality in digital mammography.