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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. [ABSTRACT FROM AUTHOR]

Background: A number of postoperative complications of navigated total knee arthroplasty (TKA) have been discussed in the literature, including tracker pin site infection and fracture. In this article, we discuss the low postoperative complication rate in a series of 3100 navigated TKAs and the overall complication rate in a systematic analysis of the literature., Methods: Three thousand one hundred consecutive patients with navigated TKAs from 2001-2016 were retrospectively evaluated for complications specific to navigation. We discuss the 2 cases of postoperative fracture through tracker pin sites that we experienced and compare this systematically with the literature., Results: Postoperatively, our 3100 patient cohort experienced a total of 2 fractures through pin sites for an incidence of 0.065%. One was a distal femoral fracture which was treated surgically, and the other was a proximal tibial fracture treated nonoperatively. Because of our incorporation of the tracker sites within our operative incision, there were no identifiable pin site infections, which others have noted at an incidence of 0.47%. Our 0.065% fracture rate compares favorably with the 0.16% rate of fracture published in the literature., Conclusion: There is an extremely low risk of perioperative complications because of the instrumentation used in navigated TKA when using the Stryker Navigation System and 4.0 mm anchoring pins placed within the surgical incision., (Copyright © 2017 Elsevier Inc. All rights reserved.)

We are reporting a series of 35 cases in which downsizing, lateralizing of the tibial baseplate and resection of the uncovered medial plateau bone releases the medial collateral ligament and tightens the lateral collateral ligament. Result in excellent ligamentous balance and correction to neutral mechanical axis. The mean follow up was 32.8 months (11-95 months) and the average pre-operative varus was 9.47° (3.5-15°) with the average post-operative alignment was 0.65° varus. We obtained a mean correction of 0.45° for every mm (millimeter) of bone resected. We did not have any varus collapse or instability. Medial Over-resection could be employed as a technique in the management of varus OA knee with 2mm of resection giving about 10 correction of deformity., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Bone mineral density (BMD), as measured by DEXA, can vary depending on bone rotation and fat content of soft tissues. We performed DEXA measurements, under controlled positioning, on 24 autopsy-retrieved femora from patients who had fully functional and asymptomatic successful TKA to determine periprosthetic BMD changes and compared results to 24 normal cadaveric femora. In TKA specimens, BMD was affected by gender, preoperative diagnosis, and zone under analysis. The lowest mean BMD was in the anterior femoral condylar zone. Males had higher mean BMD at all zones while patients with preoperative diagnosis of osteoarthritis had higher BMD in the posterior condylar zone. The mean BMD in the anterior femoral condylar zone in TKA specimens was significantly lower than in normal specimens without arthroplasties, most likely due to stress shielding., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Numerous reports have linked malaligned total knee arthroplasty (TKA) components with increased wear, poor functional outcomes, and possibly early failure due to component loosening. Consequently, proper alignment is critical to a successful outcome. This article will review: the normal mechanical alignment of the knee, classical alignment in TKA, anatomic alignment in TKA, intraoperative reference points for alignment, and the potential for new alignment schema based on the kinematic axes of knee movement. Along with our increased understanding of how the knee functions, modern total knee arthroplasty has evolved to restore a neutral mechanical axis when prostheses are implanted. Although historically the goal has been to aim to be within 3 degrees of this axis, recent reports have challenged the validity of the claim that outliers have an increased risk for revision. In addition, new alignment schemes have been developed based on the kinematic axes, but as yet we await verification of results to determine whether they increase the ability of total knee arthroplasty to provide a better-functioning and longer-lasting knee for the patient.

Purpose: The consequences of lower limb torsion deformity on knee loading in knee osteoarthritis are poorly understood. The purpose of this study was to quantify the associations between the mechanical axis, tibial torsion and knee loading in subjects with medial knee OA and in controls., Methods: Twenty-four subjects: end-staged medial knee osteoarthritis (OA) with apparent torsion deformity (TKO, n=6) and without torsion deformity (KOA, n=8) and controls (CON, n=10) were imaged using long standing lower extremity (LSLE) radiographs and computed tomography (CT). Medial knee loading was assessed using the internal knee varus moment determined by gait analysis. The LSLE mechanical axis, CT tibial torsion and the foot progression angle were used to predict medial knee loading., Results: The TKOs had significantly greater mechanical axis varus and knee varus moment compared to KOAs and CONs. The regression model predicting medial knee loading using the mechanical axis (β=0.898), tibial torsion (β=0.264) and foot progression angle (β=-0.369) showed a goodness of fit of 0.774., Conclusions: Medial knee loading was predicted by the mechanical axis and the foot progression angle. Future longitudinal studies are needed to assess the role of tibial intorsion during disease progression and following total knee replacement surgery., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A total of 1,401 primary total knee arthroplasties (TKA) were reviewed; 44 (3.2%) had at least the patellar component revised. Nine of these knees (eight patients) had insufficient bone stock to allow reimplantation of another patellar component. Clinical data on the nine knees were obtained with recent follow-up evaluation, review of their medical records and radiographs. Evaluation included Hospital for Special Surgery (HSS) scores. Average follow-up was 4 years and 7 months, 2-year range (2 months to 8 years and 4 months). Common factors found in these nine knees included: thin patella after primary TKR status, osteoarthritis, good range of motion and patella alta. Results were good to excellent in seven knees and fair in two. The untoward associations with patellectomy such as quadriceps lag, extension weakness and anterior knee pain were not experienced. Resection of the patellar component, without reimplantation, is an acceptable alternative in revision TKA lacking adequate remaining bone stock.

We present a new option for treatment of post-total knee arthroplasty periprosthetic infection associated with bone destruction and massive loss-use of an antibiotic-impregnated cement rod-spacer. This rod-spacer can be custom- made, at time of surgery, with Steinmann pins, intramedullary nails, Rush rods, Harrington spine rods, bone cement (polymethylmethacrylate), and antibiotics. We used this technique in 9 cases of periprosthetic infection over a 6-year period. The rod-spacer provided stable fixation across the knee, local antibiotic delivery, maintenance of the joint space, and preservation of soft-tissue tension around the joint through enhanced stability and length maintenance.

We report the case of a patient with recurrent periprosthetic infections after total knee arthroplasty associated with bone destruction and massive bone loss that was successfully treated with a 2-stage procedure-resection arthroplasty with insertion of an antibiotic-impregnated cement rod-spacer and systemic antibiotics and then a resection arthrodesis of the knee with the use of an intercalary allograft fixed with a long intramedullary nail. This technique is a viable option for the treatment of recurrent periprosthetic infections after total knee arthroplasty associated with bone destruction, massive bone loss, and severe instability.

This study used a cadaver model to analyze the fixation strength of 3 different patellar resurfacing preparations using an all-polyethylene patellar component. One of 3 drill hole sizes was randomly selected and used to prepare the patella. The entire construct was cemented, mounted to a servohydraulic testing machine, cycled between 0 and 50 N, and then tested to failure. Mean forces obtained prior to failure were 258.5, 293, and 353.1 N for the chamfer, 4.5-mm, and 9.5-mm drill holes, respectively. There was a statistically significant difference in strength to failure between the 9.5-mm and chamfer drill hole sizes. These findings may help to reduce patellar implant failures.

A surgeon's first response to the concept of computer-assisted orthopaedic surgery may be a sense of lost autonomy. However, a system need not and should not be designed to this end. Using the computational ability of the computer system to see beyond the human eye to view the knee with full kinematic dimensions, surgeons have recently made progress in the areas of computer-assisted ligament balancing and in using smart tools for minimally invasive surgery. Full comprehension of the use of any navigational system must begin with the understanding that the system can provide feedback that is based on only specifically programmed computer code. In referring to or locating a point or axis, the computer programmer must create an absolutely reliable methodology for determining that point or axis. Expecting the computer to achieve certain functionalities when physicians have no ironclad method to achieve such functionalities exposes the true limitations of any computer-assisted process. Although the computer generates a methodology, the process of computer-assisted surgery requires that the surgeon be constantly vigilant in analyzing the feasibility of these responses. Those instrumental in the development and implementation of computer-assisted surgical techniques must ensure that measurements are valid, precise, and reproducible across subjects and users. Prospective users of computer-assisted techniques must ensure that each of these issues has been addressed before agreeing to use the system in standard practice. Once due consideration has been given to all aspects of use, and the limitations of the system are known, the benefits of computer assistance are easily understood.

The change in coronal plane deformity throughout a range of flexion before and after total knee arthroplasty (TKA) has not been reported. Unlike most alignment assessments traditionally reporting coronal plane alignment in a standing position under static conditions, this study reports deformity throughout the flexion arc before and after deformity correction. One hundred fifty-two TKA patients using the anteroposterior axis for femoral component rotation and computer navigation techniques were included in the study. Deformity before TKA ranged from 17.5 degrees varus (deformity apex away from the midline) to 20.5 degrees valgus (deformity apex toward the midline) in full extension. Before TKA, deformity was not constant through an arc of motion and significantly decreased with flexion of 60 degrees and more (P < .01). The deformity after performing a TKA was not different (P = .478) throughout the flexion arc. The data determined that deformity is not constant throughout flexion in osteoarthritic knees preoperatively and that deformity throughout flexion can be corrected with the use of conventional alignment techniques during TKA.

Twenty-four clinically successful, autopsy retrieved porous-coated anatomic total knee arthroplasty (TKA) specimens were evaluated to determine the structure and function of the patellar meniscus. Mean implant duration was 76 months (range: 11-135 months). Histological examination showed the patellar meniscus to be composed of dense fibrous tissue with scattered regions of chronic granulomatous response to polyethylene debris. Patellar wear and polyethylene exposed patellar surface area were correlated with implant duration (r = 0.47, P = .03; r = 0.52, P = .06). Postoperative patellar tilt was also associated with patellar component wear (r = 0.64, P = .03). No other clinical measures were significantly associated with patellar wear or exposed surface area. Additional research is needed to determine what role, if any, the patellar meniscus plays in TKA outcomes.

The mechanical axis of the lower extremity was measured using preoperative long-standing radiographs in 56 patients undergoing total knee arthroplasty with the Stryker Navigation System (Stryker, Kalamazoo, Mich). Each radiograph was measured by four physicians, three times, in random order, and at delayed intervals. Measurements from each physician produced intraclass correlation coefficients of 0.9872, 0.9973, 0.9958, and 0.9839. An intraclass correlation coefficient of 0.9844 was noted between each of the raters. Pre- and postoperative axial alignments were determined with Stryker Navigation. Preoperatively, each rater overestimated deformity approximately 1 degrees (P>.05); however, postoperatively each rater underestimated the degree of deformity by approximately 1 degrees (P>.05). Measuring long-standing lower extremity radiographs provides significant inter- and intrarater reliability in determining lower extremity alignment.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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., (Copyright 2003 Elsevier Inc. All rights reserved.)

Management of an infected hip prosthesis typically requires that all associated cement be removed. In the absence of gross mantle loosening, the surgeon frequently resorts to intraoperative radiographs to assess the completeness of removal. For this reason, we undertook a study to determine limits of detection of retained cement by routine radiography. Polymethyl methacrylate bone-cement beads (Simplex-P; Stryker-Howmedica-Osteonics, Allendale, NJ) were fashioned into graduated sizes and placed within cadaver medullary canals using 2 different methods. Standard radiographic images were obtained. Individually and independently, we viewed these images and proposed the limit of resolution to be 2.4 to 3.2 mm. It is difficult to remove all cement based on radiographs alone. These results suggest a need to use techniques that permit visualization of the canal to ensure adequate cement removal., (Copyright 2002, Elsevier Science (USA). All rights reserved.)

Ligament balancing in revision settings requires attention to flexion-extension gap balancing and adjusting the asymmetry of the gaps. The tension-stress examination must be understood and done. The shortcomings of ligament tightening procedures have been experienced. Standard concave-side releases may be done, with attention given to the maintenance of adequate vascularity to the subjacent bone. However, frequently exact and sufficient balance may not be achievable, and resorting to varus-valgus constraint will be necessary. Particular emphasis has been given to the issue of controlling the flexion space and the possibility of losing that control. In the situation of loss of collateral integrity possibly exaggerated by the loss of posterior capsular integrity, one sees a gross enlargement of the flexion space. Addressing this with placement of a thicker tibial component simply leads to great flexion contracture. The larger flexion space may provide the opportunity for subluxation of the intercondylar peg of a varus-valgus constrained prosthesis. Although quadriceps tension may hold the tibia up and control the flexion space, this mechanism of stabilization will fail if the patient's knee regains substantial range of motion.

Epoetin alfa is indicated to reduce allogeneic transfusions in patients undergoing major operations. This study included 40 patients undergoing total joint arthroplasty who received 600 IU/kg doses of epoetin alfa 21, 14, and 7 days preoperatively. Statistically equal matches were obtained according to preoperative hemoglobin, operation, sex, and age. After controlling for autologous donation, the average hemoglobin level on postoperative day one in the treatment group (10.93 g/dL) was significantly higher than the matched patient group (9.86 g/dL). Likewise, treated patients were transfused with significantly less blood (0.68 units/patient) compared to the matched group (1.6 units/patient). In these patients, administration of epoetin alfa was associated with significantly higher perioperative hemoglobin levels and significantly fewer transfusions than matched counterparts. The use of epoetin alfa in this heterogeneous surgical population illustrates its success in a varied population.

The process of patellar resurfacing during total knee arthroplasty involves measuring patellar thickness. The optimal residual patellar bone thickness has been questioned. The surgeon's ability to measure patellar thickness currently rests on a standard caliper. Standard methods involve use of a smooth-mouthed caliper, which can overestimate patellar thickness because of soft tissue interposition. This brief communication introduces a new spiked caliper design that can be used to measure patellar bone thickness more accurately. Improved accuracy in measuring patellar bone thickness allows the operating surgeon to assess more correctly a patient's patellar bony status. This knowledge may result in fewer postoperative fracture complications resulting from deficiencies of bone owing to excessive resection.

The valgus knee presents a unique set of problems that must be addressed during total knee arthroplasty. Both bone and soft-tissue deformities complicate restoration of proper alignment, positioning of components, and attainment of joint stability. The variables that may need to be addressed include lateral femoral condyle or tibial plateau deficiencies secondary to developmental abnormalities, and/or wear; primary or acquired contracture of the lateral capsular and ligamentous structures; and, occasionally, laxity of the medial collateral ligament. Understanding the specific pathologic anatomy associated with the valgus knee is a prerequisite to selecting the proper surgical method to optimize component position and restore soft-tissue balance.

Previous classifications of severity for total knee arthroplasty revisions have been based largely on bone loss of the femur and tibia. These approaches failed to address the more technically difficult issues in revision surgery such as surgical exposure, contractures, extremity alignment, implant removal, soft tissue stability (in the anteroposterior and in the sagittal planes), extensor mechanism integrity, and patellar revisability. Through the Knee Society, the authors developed a severity index that incorporated these latter factors into one measure. The current authors describe the application of the Knee Society Index of Severity for failed total knee arthroplasty and its method of scoring.

Compared with primary knee replacement, total knee arthroplasty revision surgery is a more complex procedure and accounts for greater expenditures of healthcare resources at each clinical stage. Overall, patients having revision procedures have poorer functional outcomes and higher complication rates than patients having primary arthroplasty. Despite the expanded scope of revision problems and the rapidly emerging technology in revision surgery, the long-term success of any method remains in question. Because there is little consensus on the timing of revision surgery, optimal surgical reconstruction, and the type of prosthesis to be implanted, the Knee Society began development of an Index of Severity for Failed Total Knee Arthroplasty. Fifty-four percent of Knee Society members completed an 82-item questionnaire that determined their clinical impression about potential risk factors for the outcomes of revision surgery for failed total knee replacements. Using these results, a consensus group developed the final version of the index. The result of the nominal group process was the Knee Society Index of Severity, which was based on eight distinct domains. Each domain was divided into attributes and weights based on the questionnaire responses and consensus meeting. Actual case scenarios from five institutions were used to test interrater reliability and validity. The interrater reliability of the average score of all ratings was 0.95; the correlation of the criterion rating with the mean rating was 0.77. When three outliers were not included, the Pearson product correlation increased to 0.92. These data support the application of the Knee Society Index of Severity as a critical component of risk factor studies, effectiveness research, and cost-effectiveness analysis involving revisions of total knee replacements.

Since 1992, the authors have audiotaped each new patient visit and provided a copy of that tape to the patient. In addition, an office copy of the entire patient interaction is maintained in an office file. One hundred twelve patients seen over a 6-month period participated in a survey measuring their satisfaction with this procedure, and six attorneys were surveyed after listening to a representative tape. Ninety percent of patients had positive comments about receiving the tape. Seventy percent played the tape for others, most commonly their spouses. The attorneys concluded the patient was well served by this process, and there were no increased malpractice issues or exposure. The cost of providing patients with the tapes is minimal, and the high level of patient satisfaction and increased understanding offer a considerable benefit to patients and office staff.

Lower extremity osteotomy is a common procedure for managing deformity and unicompartmental gonarthrosis. One consideration not typically addressed is how the osteotomy will affect the leg length of the extremity. This article presents a numerical analysis of apparent leg-length change before and after osteotomy surgery. It also compares the differences resulting from the 3 different major types of osteotomies (closing wedge, opening wedge, and dome). Three different preoperative planning methods and a fourth intraoperative technique were studied. Using different methods of preoperative planning with the same osteotomy technique resulted in leg-length changes of 0.5 to 3 mm. Differences > 7 degrees in lower extremity alignment may result depending on the planning method used. When comparing osteotomy techniques, 2 cm in leg-length difference was calculated.

Five revision total knee arthroplasties (TKAs) involving severe femoral bone loss were performed in 1994. Each had sufficiently severe femoral bone loss in which collateral ligament origins and posterior capsular attachments were violated. A paradoxical phenomenon was observed in each case. Unlike primary TKAs, in which larger distal femoral bone resection leads to laxity of the knee joint in extension, these cases with severe distal femoral bone loss, after initial component selection, developed the opposite situation, a flexion contracture. It was hypothesized that femoral bone loss involving collateral ligament origins would permit distraction of the tibia below the femur with the knee held in flexion, but when the knee was brought to full extension, intact posterior structures would maintain a normal tibial position. To investigate this hypothesis, six fresh-frozen cadaveric lower limbs were tested in full extension and 45 degrees and 90 degrees of flexion after release of the femoral attachments of the collateral ligaments and the posterior capsule from the femur. Joint space changes were measured via a motion tracking device. Results showed that with loss of collateral attachments, 17.2+/-8.9 mm of joint space is created in 90 degrees of flexion, whereas the joint space in full extension is conserved (1.5+/-1.7 mm). With additional loss of the posterior capsule, the joint space at 90 degrees of flexion increased to 26.2+/-6.1 mm, with minimal changes in the extension gap (3.4+/-0.8 mm). Distal femoral bone loss was associated with an increase in the flexion gap compared to the extension gap.

Routine blood work that includes ESR, CRP, and glucose levels, and plain radiographs and knee aspirations are obtained from our patients who have clinical suspicion of infection. If the culture result is positive and blood tests suggest infection, the surgical plan is a two-stage revision with an interval period of intravenous antibiotic administration. Risk factors are identified, and the patient's condition optimized. An infectious disease consultant is also involved in the treatment care plan and advises the patient about the best antibiotic, management of proper antibiotic levels, and home care. If culture results are negative, cultures are repeated every week for 3 to 4 weeks after the patient stops taking antibiotics. If the cultures yield positive results, a two-stage revision protocol is initiated. In patients who have 3 to 4 negative culture results, normal blood tests and radiographs, and no history of any immunocompromised state, such as diabetes or rheumatoid arthritis, diagnoses such as polyethylene wear or synovitis can be considered. If patients have any involved risk factor or blood tests, equivocal or suggestive, isotope scintigraphy is requested. We examine tissue in patients with positive scans and equivocal blood test results with clinical suspicion of infection. We prefer an open arthrotomy, which allows us to take multiple specimens for frozen section, assess fixation of the implant, and look for any other signs of infection. If the frozen section reveals more than 10 PMNLs per high-power field, we proceed to stage 1 revision after obtaining intraoperative cultures. If an organism grows in the cultures, stage 2 protocol is initiated. If no cultures are obtained at 7 to 10 days of incubation, we may consider earlier stage 2 revision at 4 to 6 weeks (Fig. 1). In patients in whom the frozen section reveals less than 5 PMNLs per high-power field, component fixation should be assessed, and if they are loose, revision of the knee should be initiated. As with a septic revision, use of antibiotic-impregnated cement can be considered for fixation. If the components are well fixed, a polyethylene tibial tray is exchanged. In either circumstance, intraoperative cultures should be obtained, and if they yield positive results, antibiotics should be continued for 6 to 12 weeks.