Kenneth B. Mathis

Does total knee replacement restore normal knee function

Despite the advanced age of many patients having total knee arthroplasty, previous attempts to quantify patient function postoperatively have not allowed for normal deterioration of musculoskeletal function that occurs with aging. We determined the effects of aging on knee function, thereby providing a realistic level of normal, healthy knee function for patients and surgeons after total knee arthroplasties. A self-administered, validated knee function questionnaire consisting of 55 scaled multiple choice questions was used in this study. Responses were collected from 243 patients at least 1 year after they had total knee arthroplasties, and from 257 individuals (age- and gender-matched) who had no previous history of knee disorders. Many of these latter subjects reported that they could do most of the activities cited in the questionnaire without symptoms attributable to their knees. However, knee symptoms were experienced more frequently during activities that placed greater loads on the extremity. There was no difference in the knee function of men and women, and both groups had continuous deterioration in knee function with increasing age. There were large differences in the functional capacity to do activities involving the knee between the group of patients who had total knee arthroplasties and the age- and gender-matched patients with no previous knee disorders. Overall, 52% of the patients who had total knee arthroplasties reported some degree of limitation in doing functional activities, versus 22% of subjects with no previous knee disorders. Two groups of activities were identified: activities in which the patients and control subjects had essentially similar knee function (swimming, golfing, and stationary biking), and activities in which the function scores of the control group exceeded the scores of the patients who had total knee arthroplasties (kneeling, squatting, moving laterally, turning and cutting, carrying loads, stretching, leg strengthening, tennis, dancing, gardening, and sexual activity). Our data show that many of the limitations reported by patients after total knee arthroplasties are shared by individuals with no previous knee disorders. However, only approximately 40% of the functional deficit present after a total knee arthroplasty seems to be attributable to the normal physiologic effects of aging. Patients who had total knee replacements still experienced substantial functional impairment compared with their age- and gender-matched peers, especially when doing biomechanically demanding activities. This suggests that significant improvements in the procedure and prosthetic designs are needed to restore normal knee function after a total knee arthroplasty.

What functional activities are important to patients with knee replacements

There is interest in quantifying the patient’s function and mobility after joint replacement. The current study identified activities important to patients having total knee replacement and the prevalence of limitations to participation in these activities. A Total Knee Function Questionnaire consisting of 55 questions addressing the patient’s participation in various activities was developed, validated, and mailed to 367 patients at least 1 year after knee replacement. Patients were asked the frequency with which they did each activity, the activity’s importance to them, and the extent to which their participation was limited by their knee replacement. The questionnaire was returned by 176 patients, 40% men and 60% women, with an average age of 70.5 years. The most prevalent activities were stretching exercises (73%), leg strengthening exercises (70%), kneeling (58%), and gardening (57%). The activities most important to the patients were stretching exercises (56%), kneeling (52%), and gardening (50%); those most difficult were squatting (75%), kneeling (72%), and gardening (54%). The current study showed a high correlation between the importance of activities and frequency of patient participation confirming that knee replacement successfully restores a significant degree of function. However, after knee replacement, improvements in knee function still are needed to allow patients to do all activities that they consider important.

Initial Results of Managing Severe Bone Loss in Infected Total Joint Arthroplasty Using Customized Articulating Spacers

Twenty-three cases of infected total joint arthroplasty with substantial bone loss were treated with a cement spacer, which was customized intraoperatively to achieve joint stability and to allow motion. All but one of the patients were ambulatory with the spacer in place. Spacer dislocation occurred in 1 hip patient (9%) and in none of the knee patients. Articulating antibiotic-impregnated spacers with intraoperative customization is our preferred treatment of cases of infected total joint arthroplasty even in the presence of bone loss.

Surface Damage of Patellar Components Used in Total Knee Arthroplasty

BACKGROUND Patellofemoral complications are a common cause of failure of total knee replacement. In this study, we examined eighty-five patellar components that had been retrieved for a variety of reasons after a mean of 71.9 months in vivo. The objective of this study was to identify factors contributing to surface damage of patellar components in total knee replacements. METHODS The retrieved patellar components were of three primary designs: dome-shaped, sombrero-shaped, and pseudo-anatomic. Five zones on each specimen were evaluated for five different types of damage (creep, pitting, delamination, abrasion, and burnishing). The severity of the damage was assigned a score of 0 to 4, with 0 indicating no damage and 4 indicating extreme damage. The extent of the damage was also assigned a score of 0 to 4, with 0 indicating 0% and 4 indicating 76% to 100%. An asymmetry ratio was calculated for each damage pattern to evaluate the uniformity of the distribution of the damage across each component. RESULTS Eighty-six percent of the components had a damage score of > or =4 (product of the extent and severity scores) for at least one damage mechanism (creep for 38% of the components, pitting for 47%, delamination for 26%, abrasion for 49%, and burnishing for 76%). Components that had been in situ for more than two years had significantly more severe creep, delamination, and burnishing than components that had been in place for less than two years. Metal-backed designs had more severe damage than all-polyethylene components. Factors that reduced the occurrence and severity of polyethylene damage were a congruent patellar design (a non-dome-shaped component) and the use of an asymmetric femoral component. CONCLUSIONS Damage to the patellar component was a common finding, particularly when the implant had been retrieved more than two years after implantation. Moreover, delamination was frequently found on the patellar components, as has been observed by others who examined retrieved tibial inserts. The results of this study suggest that the use of congruent patellar components may reduce damage.

Making minimally invasive THR safe: conclusions from biomechanical simulation and analysis.

The use of smaller surgical incisions has become popularized for total hip arthroplasty (THR) because of the potential benefits of shorter recovery and improved cosmetic appearance. However, an increased incidence of serious complications has been reported. To minimize the risks of minimally invasive approaches to THR, we have developed an experimental approach which enables us to evaluate risk factors in these procedures through cadaveric simulations performed within the laboratory. During cadaveric hip replacement procedures performed via posterior and antero-lateral mini-incisions, pressures developed between the wound edges and the retractors were approximately double those recorded during conventional hip replacement using Charnley retractors (p < 0.01). In MIS procedures performed via the dual-incision approach, lack of direct visualisation of the proximal femur led to misalignment of broaches and implants with increased risk of cortical fracture during canal preparation and implant insertion. Cadaveric simulation of surgical procedures allows surgeons to measure variables affecting the technical success of surgery and to master new procedures without placing patients at risk.

Towards the reduction of medication errors in orthopedics and spinal surgery: Outcomes using a pharmacist-led approach

Study Design. Evaluation of medication ordering errors discovered on an orthopedic/spinal in-patient hospital unit and efforts initiated to reduce them. Objective. In this study the authors aimed to assess the frequency of medication ordering errors and to examine the impact of local measures set forth to reduce their occurrence. Summary of Background Data. Since the release of the 2000 Institute of Health report: “To Err is Human”; in-hospital medical errors have been recognized as being unacceptably high; the consequence being preventable death rates estimated near 125,000 patients per year. The most common of errors are those involving medications. Methods. The study consisted of 2 parts. In part 1, the charts from 82 consecutive patients admitted to the Orthopedic/Spine Surgical Unit were assessed to determine the frequency, type, and potential severity of medication ordering errors. Several programs to reduce such errors were subsequently instituted and included: improved chart surveillance by pharmacists, a newly developed medication/history form given to and reviewed with patients before surgery, in-service education of preoperative nursing staff, patient database form changes, and requests for patients to bring their medications on admission. Part 2, including 87 patients, assessed the impact of these measures. Results. In part 1, medication errors were detected in 62% of orders overall. Of these, 43% were found to be of moderate or high potential for harm. After the institution of the above measures (part 2), overall errors were reduced by 31%; moderate/high risk potential harm was reduced by 64%; and errors of omission were detected twice as often. Conclusion. Medication errors in ordering are common in orthopedics. We found in part 1 that a chart review and patient interview by the pharmacy team can detect and correct these before reaching the patient. Furthermore, we found in part 2 that the risk could be further reduced by the implementation of pharmacist-led: patient education, education of preoperative nursing personnel, improvement of forms used for data collection, and having the patients bring all of their medications on admission.

Extraarticular abrasive wear in cemented and cementless total knee arthroplasty.

In this study, we examine the contributions of periprosthetic impingement to a seldom recognized source of PE damage resulting in gouging, abrasion, and severe localized damage in cemented and cementless total knee replacement. One hundred sixty two tibial components of 34 different designs in a retrieval collection were examined. The presence and location of abrasive wear to the nonarticulating edges of the insert were measured, with representative specimens examined using SEM. Significant abrasive wear was observed in 35% of the retrievals with cemented femoral components and 25% from noncemented components. Within the group of worn inserts, abrasive scars were seen with a frequency of 75% on the extreme medial edge, 20% on the extreme lateral edge, 26% on the posteromedial edge, and 16% on the posterolateral edge. The role of extraarticular impingement in this damage mode was confirmed by examination of retrieved femoral components with overhanging cement or embedded osteophytes. In the majority of cases, this complication may be avoided by careful removal of excess cement and extracortical osteophytes.

A computerized bioskills system for surgical skills training in total knee replacement

Abstract Although all agree that the results of total knee replacement (TKR) are primarily determined by surgical skill, there are few satisfactory alternatives to the ‘apprenticeship’ model of surgical training. A system capable of evaluating errors of instrument alignment in TKR has been developed and demonstrated. This system also makes it possible quantitatively to assess the source of errors in final component position and limb alignment. This study demonstrates the use of a computer-based system to analyse the surgical skills in TKR through detailed quantitative analysis of the technical accuracy of each step of the procedure. Twelve surgeons implanted a posterior-stabilized TKR in 12 fresh cadavers using the same set of surgical instruments. During each procedure, the position and orientation of the femur, tibia, each surgical instrument, and the trial components were measured with an infrared coordinate measurement system. Through analysis of these data, the sources and relative magnitudes of errors in position and alignment of each instrument were determined, as well as its contribution to the final limb alignment, component positioning and ligament balance. Perfect balancing of the flexion and extension gaps was uncommon (0/15). Under standardized loading, the opening of the joint laterally exceeded the opening medially by an average of approximately 4 mm in both extension (4.1 ± 2.1 mm) and flexion (3.8 ± 3.4 mm). In addition, the overall separation of the femur and the tibia was greater in flexion than extension by an average of 4.6 mm. The most significant errors occurred in locating the anterior/posterior position of the entry point in the distal femur (SD = 8.4 mm) and the correct rotational alignment of the tibial tray (SD = 13.2°). On a case-by-case basis, the relative contributions of errors in individual instrument alignments to the final limb alignment and soft tissue balancing were identified. The results indicate that discrete steps in the surgical procedure make the largest contributions to the ultimate alignment and laxity of the prosthetic knee. Utilization of this method of analysis and feedback in orthopaedic training is expected rapidly to enhance surgical skills without the risks of patient exposure.

An Orthopedic Perspective of Osteoporosis

Publisher Summary The clinical significance of osteoporosis is overwhelmingly related to fracture events in affected patients. Management of these fractures comprises a large portion of the efforts of nearly all practitioners of orthopedic surgery. The goal of treatment of any osseous injury is a rapid return to normal function. This almost always includes an interval of immobilization of the injured bone by externally applied casts or braces or internally stabilizing it by operatively placed internal fixation devices. A disappointing number of fractures occur within or adjacent to articular surfaces. Accurate reduction of intraarticular fracture fragments and preservation of motion in the joint are important treatment objectives. Displacement of non-articular fractures can also have important functional significance; translational, angular, and rotational deformities may also add complexity to the problems of a fracture management program. Surgical management of a patient with an acute fracture, where decreased mineral density is suspected, should include an assessment of fracture risk and appropriate treatment and counseling for the patients overall osteoporotic condition as well as his or her recent fracture. Immediately following fracture, the hospital environment is an excellent place to initiate counseling with regard to diet, calcium and vitamin D supplementation, and potential anti-resorptive therapies. A bone mineral density examination should be considered. The fracture event provides an opportunity to initiate ongoing treatment for bone fragility, which should continue long after hospital discharge.

CAOS for technical skills training in orthopaedic surgery

accepted as a source of simulated reality which is all pervasive in television, advertising, and entertainment. This same technology has made some in roads into education, however, in the orthopedic context, our primary exposure to the potential of computers has been in Surgical Navigation, which is based on the fundamental premise that computerbased systems should be indispensable components of the process of performing surgery. An alternative approach is based on the belief that the goal of all efforts in surgeon training should be empowerment of the surgeon through development of surgical skills, without long-term dependence on technology to implement a surgical plan. Rationale for this approach can be found in the classic field of motor learning, where it has been long established that, aside from practice, information about performance, in the form of both intrinsic and extrinsic feedback, is the single most important variable affecting outcome [6]. The precise format of this information, how much of it is fed back to the performer, and the timing of its presentation all affect performance and learning. In learning a motor skill, it has been shown that terminal feedback in the form of knowledge of results (feedback on the movement outcome in terms of the environmental goal) and knowledge of performance (feedback on the movement itself ) can be more effective than concurrent feedback, or guidance, presented during the task itself. Guidance feedback has been shown to have the strongest effects on performance during the trials in which it is administered [7–9] as opposed to the more permanent changes attributed to motor learning achieved through post-performance feedback [10]. In fact, it has been suggested that a heavily guiding form of feedback (»enabling«) is actually detrimental to learning [11].  