Kenneth Greene

Anthropometric Measurements of the Human Knee: Correlation to the Sizing of Current Knee Arthroplasty Systems

Background: There is a paucity of data concerning the morphological dimensions of the distal part of the femur, the proximal part of the tibia, and the patella. The objective of this study was to analyze the exact anatomic data collected from a large group of patients undergoing total knee arthroplasty and to correlate the measurements to the dimensions of current prosthetic systems. Methods: Eight different centers collected morphologic data from the distal part of the femur, the proximal part of the tibia, and the patella from 337 knees during total knee arthroplasty. Microcaliper measurements from templates and measuring guides were used to decrease intraobserver variation. The study included 188 women (209 knees) and 107 men (128 knees) who had a mean age of sixty-nine years. A characterization of the aspect ratio (the medial-lateral to anterior-posterior dimensions) was made for the proximal aspect of the tibia and the distal part of the femur. Known dimensions from six prosthetic knee systems were compared with the morphologic data. Results: A wide variation in the aspect ratio for the femoral component was seen among the six different prosthetic systems. For women, there was a significant association between the component size and the amount of medial-lateral overhang, with larger sizes having more overhang (p < 0.0001). Although the femoral aspect ratio for the morphologic data showed higher ratios for smaller knees and proportionally lower ratios for larger knees, the designs showed little change in the aspect ratio. The tibial aspect ratio from the morphologic data showed a higher ratio for smaller knees and a proportionally lower ratio for larger knees. The Duracon component tracked the decline in aspect ratio fairly well, whereas the other brands either did not change with anterior-posterior dimension or actually increased (NexGen). Gender differences in the morphologic data were shown by the variable tibial aspect ratios. A comparison of the bone dimensions from the study data and the dimensions of the implants indicated that the smaller sizes were too small while the larger sizes tended to be too large. The average overall unresected patellar thickness was 23.7 mm. Conclusion: The results of this study will allow manufacturers to make more appropriate determinations of the sizes and aspect ratios of components for use in total knee arthroplasty.

Symptoms of postsurgical distress following total knee replacement and their relationship to recovery outcomes

OBJECTIVE Prior research has suggested that posttraumatic stress symptoms may occur in the context of medical events. Further, these symptoms are often comorbid with conditions associated with pain. Therefore, the current study examined the occurrence of distress following arthroplastic surgery and the relationship of these symptoms to postoperative recovery. METHODS Patients (N =110) undergoing unilateral, total knee replacement (TKR) surgery were assessed at three time points proximal to their surgery: approximately 2 weeks prior to surgery (T1), 1 month following surgery (T2) and 3 months following surgery (T3). Patients completed survey assessments of recovery outcomes (Western Ontario and McMaster Universities Osteoarthritis Index) and distress (The Impact of Event Scale [IES]) following surgery (T2 and T3). RESULTS A significant percentage (20%) of patients undergoing TKR reported noteworthy levels of postsurgical stress 1 and 3 months following surgery. Further, this distress was associated with a more difficult recovery following TKR, characterized by more severe pain and greater functional limitations. After controlling for potential confounding variables, regression analyses suggested that postsurgical stress was cross-sectionally related to pain perception and longitudinally predicted subsequent functional limitations and global assessments of recovery. DISCUSSION To our knowledge, this is the first study to examine postoperative distress (using the IES) following TKR. The present study adds to the growing body of literature documenting the impact of psychological processes on postoperative recovery.

A Prospective, Longitudinal Study of Patient Satisfaction Following Total Knee Arthroplasty Using the Short-Form 36 (SF-36) Survey Stratified by Various Demographic and Comorbid Factors

The purpose of this study was to evaluate the longitudinal variations in SF-36 physical and mental scores and the effects of demographics and comorbidities after TKA. This prospective study evaluated 108 men and 173 women who had a mean age of 66 years. All patients were followed for a minimum of five years and SF-36 physical and mental component scores were evaluated longitudinally. Physical scores steadily increased during the first year whereas mental component scores initially decreased in the first six weeks and then subsequently increased and both plateaued at one year. Demographic and social factors had a greater effect on physical component scores and comorbidities were more predictive of poor mental scores. Surgeons should counsel their patients that they will likely perceive the full benefit of TKA by one year, but in the first months may perceive worse outcomes.

Clinical and Patient-reported Outcomes of Primary TKA With a Single-radius Design

Total knee arthroplasty (TKA) is a cost-effective procedure used to treat degenerative knee disease with excellent long-term outcomes. However, TKA has not always resulted in excellent functional and patient satisfaction outcomes, partly due to the use of prostheses that did not reproduce natural knee kinematics. Due to a paucity of reports on single-radius designs, the authors evaluated the clinical and patient-reported outcomes of primary TKA in patients who had received a single-radius prosthesis. A total of 287 TKAs from 7 centers were prospectively evaluated. Mean follow-up was 5 years, with each patient undergoing year re-evaluation. Kaplan-Meier implant survivorship was 99.7% at a final follow-up of 7 years. The total reoperation rate was 1.4%. Clinical outcomes demonstrated significant improvements in Knee Society, Short Form 36, and activity scores at a mean follow-up of 5 years. The authors believe that various features of this prosthesis may have contributed to these excellent outcomes. Further longer-term studies are necessary to better evaluate these outcomes.

Predicting symptoms of post-traumatic stress among patients undergoing orthopedic surgery on the basis of routinely collected cardiovascular data

The present study examined whether in-hospital assessments of heart rate and blood pressure predicted symptoms of post-traumatic stress (PTS) in 110 patients undergoing total knee replacement surgery. After controlling for conceptually relevant factors, in-hospital cardiovascular functioning predicted symptoms of PTS three months following surgery. Specifically, lower pre-surgical and post-surgical systolic and diastolic blood pressure predicted more symptoms of avoidance and PTS (total). In contrast, higher heart rate prior to and shortly following surgery predicted marginally more intrusive thoughts. The present findings suggest that routinely collected medical data may provide a means to identify patients at risk for problematic outcomes following surgery.

Bilateral Symmetrical Comparison of Femoral and Tibial Anatomic Features.

BACKGROUND Variability in morphologic features of the human lower extremity within and across populations has been reported, but limb asymmetry within individuals is often overlooked. For example, in 19 studies of version of the lower extremity in the literature, 6 document asymmetry in the population, but none of these reports document asymmetry in an individual. The aim of this study was to identify the (a)symmetry and quantify variability in the tibiae and femora of matched pairs of limbs. More specifically, using a computed tomography scan database tool, we (1) identified (a)symmetry between paired left and right legs for angulation, version, and alignment features and (2) calculated the percentage of paired limbs with >1° of (a)symmetry for each evaluated parameter. METHODS Computerized axial tomographic scans (<1.0 mm slices) from bilateral lower limbs of 361 skeletally mature subjects without bone pathology were prospectively acquired. Bones were segmented and morphologic features were measured. RESULTS Angular features are symmetric left to right, but rotational features are not, with 7° of mean asymmetry in femoral anteversion (range: 0°-23°) and 3° of asymmetry in tibial version (range: 0°-8°). CONCLUSIONS This study disproves the hypothesis that human limbs are absolutely symmetric, confirming instead that there is asymmetry in version between left and right paired limbs. Surgeons strive for symmetry in lower extremity reconstruction, and they often compare side to side in outcome studies, believing that normal limbs are absolutely symmetric when this is not necessarily true. These assumptions concerning lower extremity symmetry need to be reassessed.

Physiological Indices of Stress Prior to and Following Total Knee Arthroplasty Predict the Occurrence of Severe Post-Operative Pain

OBJECTIVE The severe pain and disability associated with osteoarthritis often motivate individuals to undergo arthroplastic surgery. However, a significant number of surgical patients continue to experience pain following surgery. Prior research has implicated both the hypothalamic-pituitary-adrenal (HPA) axis and sympathetic nervous system (SNS) in the sensitization of pain receptors and chronic pain conditions. This study uses a prospective, observational, cohort design to examine whether physiological stress responses before and after surgery could predict post-operative pain severity. SUBJECTS Participants included 110 patients undergoing total knee arthroplasty. METHODS Physiological indices of stress included the measurement of catecholamine and cortisol levels in 15-hour urine samples collected prior to and 1 month following surgery, as well as in-hospital heart rate and blood pressure (before and after surgery), which were abstracted from medical records. Patients completed the pain subscale of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) [Bellamy et al., J Orthop Rheumatol 1: , 95 (1988)] 2.5 weeks prior to surgery and at a 3-month follow-up. RESULTS Contrary to expectations, lower stress hormone levels at baseline were related to more severe post-operative pain. Data at later time points, however, supported our hypothesis: cardiovascular tone shortly before surgery and urinary levels of epinephrine 1 month following surgery were positively related to pain severity 3 months later. CONCLUSION Results suggest that the occurrence of post-operative pain can be predicted on the basis of stress physiology prior to and following arthroplastic surgery.

Using established predictors of post-traumatic stress to explain variations in recovery outcomes among orthopedic patients

The present studies examine whether information contained in medical records can be used to predict outcomes following two orthopedic procedures: repair of hip fracture and total knee replacement. Study 1 reports the acute, in-hospital recovery data from the medical records of 119 hip fracture patients. Study 2 is a prospective, longitudinal investigation of 3-month postoperative recovery of 110 total knee replacement patients. Patients characterized by a greater number of post-traumatic stress risk factors experienced poorer outcomes following orthopedic surgery. Our results suggest that patients at risk for negative outcomes can be identified by information readily available to medical personnel.