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Biomedical subjects

Kenneth A Krackow

Publications and source records attributed to Kenneth A Krackow.

At least 19 recordsLinked to original sources
PubMed2006

Differences between extramedullary, intramedullary, and computer-aided surgery tibial alignment techniques for total knee arthroplasty.

Traditionally, intramedullary and extramedullary tibial alignment techniques are used to obtain neutral alignment during total knee arthroplasty. Computer-assisted techniques are available to aid in obtaining alignment intraoperatively. This study analyzed the difference in tibial alignment using intramedullary and extramedullary techniques, and compared them to the resulting tibial axis as determined by a computer navigation system. The tibial alignment standard measure was determined by a spiral computed tomography (CT) study of each lower extremity. Intramedullary techniques resulted in a 1.3 degrees +/- 1.4 degrees of varus alignment and 4 degrees +/- 2.1 degrees increase in posterior slope while the extramedullary techniques resulted in 1.5 +/-1.8 degrees of valgus alignment and 1.8 degrees +/-1.1 degrees increase in posterior slope compared to the navigation system alignment. Direct measurement of metal markers on CT-scan analysis using the navigation system resulted in <0.5 degrees difference from the navigation data. Although the traditional alignment techniques are within a few degrees, the addition of the errors in all planes gives a much higher degree of error. Direct measurement of the mechanical axis using computer-guided surgical techniques for the tibia give a greater degree of accuracy compared to traditional alignment techniques.

Arthroplasty, Replacement, Knee↗
PubMed2006

Flexion and extension gap balancing in revision total knee arthroplasty.

UNLABELLED: Revision total knee arthroplasty presents a unique set of problems when attempting to balance flexion and extension gaps. Loss of soft tissue support and established deformity can make balancing difficult. One needs to balance the flexion and extension gap heights as well as medial and lateral symmetry, which may not always be attainable. We used a set of stepwise techniques to reestablish the joint line in extension using femoral augments, and then balanced the flexion gap using different sized femoral components. We retrospectively analyzed 45 patients who had revision total knee replacement with an average of 4 years followup. These patients had a mean flexion of 105 degrees and none had signs of instability in flexion or extension or on clinical exam. Despite the complex nature of revision knee arthroplasty, cases utilizing an algorithm to balance the extension and flexion gaps, with increased implant constraint when necessary, can aid in obtaining a good outcome. LEVEL OF EVIDENCE: Therapeutic study, level IV (case series). See Guidelines for Authors for a complete description of levels of evidence.

Aged↗
PubMed2006

Extensor mechanism disruption after total knee arthroplasty.

UNLABELLED: Extensor mechanism disruption after total knee arthroplasty is a challenging complication for orthopaedic surgeons. The treatment options for repair include observation, direct primary repair, direct primary repair with synthetic ligament or autogenous tissue augmentation, or reconstruction with allograft tissue. A computerized systemic review and literature search was performed to identify the relevant literature on extensor mechanism disruptions associated with total knee arthroplasty. A comprehensive review of the literature and description of relevant treatment options and outcomes were performed using the information gained with the literature review. A multi-center prospective study on a consecutive series of patients recruited from the North American Knee Arthroplasty Revision (NAKAR) study was performed and data collected pre-operatively, intra-operatively, and post-operatively on patients that had a failed total knee arthroplasty using validated health related quality of life measures was analyzed. Six out of 290 patients in the study had extensor mechanism disruption and this group of patients had overall worse functional outcomes. The results of the study have solidified our knowledge that patients with extensor mechanism disruptions have worse functional outcomes and will need intensive management and rehabilitation. LEVEL OF EVIDENCE: Economic and decision analyses, level III (systematic review of level III studies). See Guide for Authors for a complete description of levels of evidence.

Arthroplasty, Replacement, Knee↗
PubMed2006

Effect of one- and two-pin reference anchoring systems on marker stability during total knee arthroplasty computer navigation.

OBJECTIVE: This study investigated different infrared marker reference base attachments in cadaveric bone and their effects on alignment outcome when different loads were applied. MATERIAL AND METHODS: Five cadaveric specimens were used to test four reference base attachments: a locking one-pin (4.0 mm and 5.0 mm pins) and a two-pin clamp (Hoffman fixator, 3.0 mm and 5.0 mm pins, Stryker Inc., NJ). Each was tested with metaphyseal and diaphyseal attachments. A navigation system (Stryker Navigation, MI) was used for testing with applied incremental loads and torques (65 N and 1.0 Nm) to the different reference base configurations. RESULTS: With 65 N the maximum change in distance to a verification point was 4.3 + 1.6 mm with the 4.0 mm locking pin in metaphyseal bone. No difference in verification point distances was found with any two-pin configuration. Alignment changes greater than 4 degrees resulted with the 65 N loads and a 4.0 mm pin. CONCLUSION: The results may prove beneficial in comparing the resulting error of different manufacturers and allow surgeons to realize the variability that may occur through incidental contact in the operating room.

Arthroplasty, Replacement, Knee↗
PubMed2006

Pelvic tracker effects on hip center accuracy using imageless navigation.

OBJECTIVE: Imageless computer assisted total knee surgical systems have commonly relied on determination of the functional rotational center of the femoral head as a landmark for determining the lower extremity mechanical axis. This has been accomplished through range of motion and center of rotation calculations for the femur with respect to the pelvis as the lower extremity is taken through a range of motion. Our study evaluated the use of this algorithm with and without a pelvic tracker attached to the iliac crest. MATERIALS AND METHODS: The functional center of the hip joint was also compared to the true radiographic center as determined by spiral CT data. Evaluating the different methods on six lower extremities from three whole-body cadavers revealed significant differences in the location of the calculated hip joint center, but little difference in the resulting lower extremity mechanical axis determination. The functional hip joint centers measured with and without a pelvic tracker differed from one another and from the CT-determined hip center. RESULTS: No differences were found in the coronal plane measurements, but statistically significant differences were found in the sagittal plane measurements. CONCLUSION: Algorithms that reduce the noise generated by pelvic movement should be devised to eliminate the need for a pelvic tracker.

Algorithms↗
PubMed2005

The variability of intramedullary alignment of the femoral component during total knee arthroplasty.

Intramedullary instrumentation for femoral component alignment during total knee arthroplasty is readily used. Newer alignment techniques using computer navigation are now available. This study assesses the difference in the sagittal and coronal plane alignments using a cadaveric model with 3 different entry points for intramedullary alignment compared with a navigation system. Seven cadaveric limb's results show that the anterior starting point resulted in recurvatum (-2.2 degrees +/- 1.4 degrees ), the middle starting point resulted in 1.9 degrees +/- 2.2 degrees of flexion, and the posterior starting point in 3.8 degrees +/- 2.6 degrees of flexion compared with the calculated femoral axis by the computer navigation system. When comparing the valgus angle, no statistical difference between any methods resulted (average 5.2 degrees +/- 0.9 degrees valgus). The anterior and posterior starting points were significantly different in the sagittal plane. These data suggest that alignment can be significantly affected by the starting point chosen for intramedullary instrumentation.

Arthroplasty, Replacement, Knee↗
PubMed2005

Antibiotic-laden cement: technique for uniform manual mixing.

The use of polymethyl methacrylate has revolutionized surgical technique in total joint arthroplasty. In addition, in an effort to reduce the rate of infections as well as to treat active infections, the practice of adding powdered antibiotics to the cement has become commonplace. A simple and efficient technique of mixing antibiotic powder into cement that creates a uniform distribution of antibiotic is introduced. In addition, this process reduces the presence of "antibiotic voids," which, if present can alter the physical properties of the cement itself.

Anti-Bacterial Agents↗
PubMed2005

Development and validation of a lower-extremity activity scale. Use for patients treated with revision total knee arthroplasty.

BACKGROUND: Valid outcome measurement tools are required to reliably demonstrate the effectiveness and clinical outcomes of lower-extremity arthroplasty. Having ascertained a lack of a practical and valid measure of the change in actual daily physical activity that occurs prior to and following lower-limb arthroplasty, we developed and validated a lower-extremity activity scale. METHODS: The eighteen-level self-administered scale was developed with the aid of content experts to ensure face validity. Validity and reliability were assessed with the use of (1) pedometer measurements of seventy subjects over seven days; (2) next-of-kin proxy measurements of the activity levels of ninety patients before they underwent lower-limb arthroplasty; and (3) application, and correlation with the Western Ontario and McMaster Universities Osteoarthritis Index scores, in a prospective seventeen-center clinical study of 297 consecutive patients undergoing revision total knee arthroplasty. In this latter study, demographic and comorbidity data were also collected. Univariate and bivariate correlations were performed, and a multivariate structured equation modeling approach was used to further test responsiveness, reliability, and validity of the lower-extremity activity scale. RESULTS: Pedometer readings correlated with the activity levels derived with the lower-extremity activity scale (r = 0.79). Of note was the finding that age, weight, and body mass index did not correlate well with the average number of steps per day (r = -0.32, -0.32, and -0.25, respectively). A significant correlation was found between the lower-extremity activity scores recorded by the patients and those reported by their next of kin (Pearson correlation, r = 0.715; p = 0.0001) and between the initial lower-extremity activity scores and two-week-retest scores (intraclass correlation = 0.9147; p < 0.0001), demonstrating the validity and reliability of the scale. The lower-extremity activity scale was responsive, accurately reflecting changes in the patient's condition between baseline and the time of follow-up (p < 0.001), and it was reliable, with baseline values correlating with follow-up scores (p < 0.001). The convergent validity of the lower-extremity activity scale was established by correlations with the function scores (r = -0.301, p < 0.001) and pain scores (r = -0.241, p < 0.001) derived with the Western Ontario and McMaster Universities Osteoarthritis Index and with a higher number of comorbidities (r = -0.244, p < 0.001). Multivariate path modeling further demonstrated diminished activity in patients who had more difficulty in functioning and a greater number of comorbidities. CONCLUSIONS: We developed a lower-extremity activity scale and validated that it was an effective instrument for the assessment of patients' actual activity levels. It is easy to apply and interpret, and it is valid and ready for use in the clinical setting. This scale will allow more accurate analysis and prediction of outcomes. Consequently, it will become a useful, practical adjunct to objective clinical decision-making and intervention for patients undergoing arthroplasty.

Activities of Daily Living↗
PubMed2004

Proximal tibial osteotomy: where did you go?

The prevalence of knee osteotomy seems to have diminished. Better total knee arthroplasty (TKA) results, greater survival, increased use of unicompartmental arthroplasty, and decreased surgeon confidence for osteotomy are likely causes. However, continued use of knee osteotomy is encouraged by this author. TKAs are not perfect. Furthermore, there is limited long-term durability data for younger, active patients. At 40 to 60 years of age at the time of surgery, some patients will need prosthetic replacements that must last up to 40 to 60 years. A case is made for performing an osteotomy earlier rather than later. Regarding TKA after proximal tibial osteotomy, the difficulty and inappropriateness of the standard comparisons are clear. Comparison of a virgin primary knee at one point in time, with a patient whose situation led to osteotomy surgery 5 to >10 years earlier is not a matched comparison. It is proposed that future biologic resurfacing, together with computer-and even robotic-methods, as well as other advances in biology and technology, will combine to resurrect the performance of knee osteotomies.

Adult↗
PubMed2004

In-hospital deaths following elective total joint arthroplasty.

Elective hip or knee arthroplasty is considered a relatively safe orthopedic procedure. However, given the number of procedures performed, catastrophic complications, such as death, occur. Between January 1995 and March 2001, 3438 patients underwent elective hip or knee arthroplasty at our institution. Patients with diagnoses of fracture or malignancy were excluded. Extensive chart reviews were performed on 9 postoperative deaths. The American Society of Anesthesiologists (ASA) score was significantly related to the incidence of postoperative death. Specifically, ASA class III patients were more likely to encounter postoperative death. Additionally, a higher rate of postoperative complications occurred in the deceased group.

Aged↗
PubMed2003

Enhancing femoral cement fixation in total knee arthroplasty.

Several factors have been shown to be associated with early development of radiolucent lines at the bone-cement interface in total knee arthroplasty (TKA). The posterior condylar surfaces, in particular, seem subject to poor cement technique, which could lead to early loosening. This study compares two cementation techniques in TKA, with respect to depth of cement penetration and radiolucency in the posterior condyles. All penetration depths were greater in group I (injected) versus group II (noninjected). Sixty-seven percent of group I showed penetration depths >1.5 mm compared with 23% of group II. No specimen in group I had gaps in the cement mantle on visual inspection or radiolucency on radiographic evaluation. No statistical differences, however, could be demonstrated between the two groups.

Arthroplasty, Replacement, Knee↗
PubMed2003

Instability in total knee arthroplasty: loose as a goose.

As total knee arthroplasties last longer and are used in younger patients, as well as for a variety of other reasons, greater interest in postoperative tibiofemoral instability has developed. Initial evaluation emphasizing correlation of symptoms and findings together with elucidation of the specifics of the instability are mandatory. Gap inequality, gap asymmetry, and the causes of each are noted. Soft tissue repair or reconstruction alone has not been very successful for such instabilities. Some aspect of revision with component change is generally necessary, and some correction of alignment, gap features, and other issues, with advancement to a higher order of constraint, will generally be necessary.

Arthroplasty, Replacement, Knee↗