Posterior Compartment Debridement and Varus Deformity Correction in Total Knee Arthroplasty.

BACKGROUND: Restoration of joint-line position and deformity correction remain important tenets for preserving stability and function after total knee arthroplasty (TKA). We sought to characterize the role of posterior osteophytes in the correction of alignment deformity during TKA. METHODS: We evaluated 57 patients (57 TKAs) who participated in a trial of robotic-arm assisted TKA outcomes. Weight-bearing and fixed preoperative alignment was measured using long-standing radiographs and tools of the robotic-arm tracking system, respectively. Total volume (cm3) of posterior osteophytes was quantified using preoperative planning computed tomography scans. Joint-line position was evaluated using bone resection thicknesses measured using a caliper. RESULTS: The mean (minimum to maximum) initial fixed deformity was 4 degrees (range, 0 to 11) of varus. All patients showed asymmetric posterior osteophytes. Mean total osteophyte volume was 3 cm3 (range, 1 to 9). Total osteophyte volume was positively correlated with severity of fixed deformity (r = 0.48, P = .0001). Removal of osteophytes allowed for the correction of functional alignment to within 3 degrees of neutral in all cases (mean 0 degree), with none requiring release of the superficial medial collateral ligament. Tibial joint-line position was restored to within 3 millimeters in all but 2 cases (mean increase of height, 0.6 [range, -4 to +5]). CONCLUSION: In the end-stage diseased knee, posterior osteophytes typically occupy space in the posterior capsule on the concave side of the deformity. Thorough debridement of posterior osteophytes may help facilitate management of modest varus deformity with decreased need for soft-tissue releases or adjustments to planned bone resection.

Increased Prevalence of Posterior Cruciate Ligament Dysfunction Noted With 3-Dimensional Intraoperative Kinematic Evaluation in Total Knee Arthroplasty.

BACKGROUND: Poor restoration of cruciate-driven kinematics after total knee arthroplasty may result from technical difficulties, but the ligament may also be functionally compromised by the presence of arthritis. We asked whether the function of the posterior cruciate ligament (PCL) could be assessed intraoperatively to predict the quality of the resulting posterior cruciate kinematics. METHODS: PCL integrity was assessed using intraoperative infrared trackers to monitor knee kinematics in 73 patients. Three-dimensional images of the femur and tibia were projected onto a screen, allowing the surgeon to visualize kinematic relationships in real time. We measured femoral rollback (distance of femoral contact as a percentage of antero-posterior tray width) from images captured by the robotic system during initial kinematic assessment, gap balancing, and assessment of the final construct and from lateral flexion radiographs obtained 2 years after surgery. Associations were characterized using Pearson's correlation and graphical methods. RESULTS: Thirty-six knees (49%) showed rollback <60% during gap balancing, indicative of PCL insufficiency. The rollback during gap balancing was positively correlated with that seen in the final cruciate retaining constructs (r = 0.60, P < .001), which in turn predicted rollback 2 years after surgery on lateral flexion X-rays (r = 0.50, P = .006). CONCLUSION: Intraoperative functional evaluations can allow the surgeon to identify cases where rollback is not consistent with desirable knee kinematics, and posterior stabilization may lead to a better outcome for those patients.

Lower limb kinematics of unicompartmental knee arthroplasty individuals during stair ascent.

OBJECTIVE: Purpose of the study was to compare lower-limb kinematics and interlimb asymmetry during stair ascent in individuals post-medial or lateral unicompartmental knee arthroplasty (UKA). METHODS: 60 patients (20 medial; 10 lateral) post-UKA and 30 matched healthy controls performed stair ascent. Spatio-temporal, lower-limb kinematics and interlimb asymmetries during stair ascent were compared. RESULTS: Medial-UKA group displayed 5° less knee extension of the UKA limb than controls (p = 0.005) and 2° less than the contralateral limb during stance phase. No interlimb asymmetries were found for lateral-UKA. CONCLUSION: Patients post-UKA demonstrate satisfactory lower-limb kinematics and minimal interlimb asymmetry during stair ascent compared to healthy individuals.

Incidence of venous thromboembolism following initiation of non-steroidal anti-inflammatory drugs in U.S. women.

OBJECTIVE: To evaluate the risk of venous thromboembolism (VTE, i.e. deep vein thrombosis or pulmonary embolism, or both) following new use of NSAIDs in a long-term cohort of U.S. women. METHODS: We investigated initiation of coxibs and traditional NSAIDs (excluding aspirin) and incident VTE in 39 876 women enrolled in the Women's Health Study from 1993-95 and followed with yearly questionnaires until 2012. We defined initiation as the first reported use of NSAIDs for ≥4 days per month. Incident VTE was confirmed by an end point committee. We estimated hazard ratios (HRs) and risk differences (RDs, expressed as percentages) comparing NSAID initiation with non-initiation and acetaminophen initiation (active comparator) via standardization using a propensity score that incorporated age, BMI, calendar time, and relevant medical, behavioural, and socioeconomic variables updated over time. RESULTS: The HR (95% CI) for risk of VTE in the as treated analyses comparing initiation with non-initiation, was 1.5 (1.2, 1.8) for any NSAID, 1.3 (1.1, 1.7) for traditional NSAIDs, and 2.0 (1.3, 3.1) for coxibs, with 2-year RDs 0.11, 0.08 and 0.32, respectively. When comparing the risk of VTE after initiation of any NSAID with that after acetaminophen initiation, the HRs were 0.9 (0.6, 1.5), 0.9 (0.5, 1.5) and 1.4 (0.6, 3.4), with 2-year RDs 0.03, -0.01, and 0.13, respectively. CONCLUSION: New use of NSAIDs was associated with increased VTE risk compared with non-use, but the association was null or diminished when compared with acetaminophen initiation. Elevated VTE risks associated with NSAID use in observational studies may in part reflect different baseline risks among individuals who need analgesics and may overstate the risk patients incur compared with pharmacologic alternatives.

Changing predictors of statin initiation in US women over two decades.

PURPOSE: To describe changing roles of predictors of statin initiation before and after incident coronary heart disease, and before and after publication of National Cholesterol Education Program Adult Treatment Panel-III (ATP-III) guidelines in a cohort of US women. METHODS: We identified 34 382 women enrolled into the Women's Health Study from 1993 to 1995 and followed up until 2012. Proportions of previous nonusers initiating statins were described over time. We used multivariable linear regression models to estimate adjusted initiation proportion differences (IPDs) for initiation overall, separately before and after incident coronary heart disease, and separately for ATP-II and ATP-III time periods. RESULTS: Key predictors of initiation overall were self-reported total cholesterol, and previous incident coronary heart disease, cerebrovascular disease, and diabetes. Adjusted IPDs (percentage) for total cholesterol > 240 vs <200 mg/dL were 7.5 (95% confidence interval [CI], 7.0-8.0) and 9.3 (95% CI, 8.7-9.9) during ATP-II and ATP-III time periods, respectively. Adjusted IPDs in women with diabetes were 7.0 (95% CI, 6.3-7.8) and 11.9 (95% CI, 6.7-17.0) for primary and secondary prevention, respectively, and 3.1 (95% CI, 2.1-4.0) and 9.2 (95% CI 8.2-10.2) for before and after ATP-III, respectively. CONCLUSIONS: Secular trends reflected evolution toward risk factor-based treatment indications for statin initiation with increased initiation among diabetics and women with normal and borderline cholesterol. The role of serum cholesterol changed over time, though the character was scale (multiplicative vs additive) dependent. In pharmacoepidemiologic studies of statins, strength of confounding by important variables sometimes unmeasured in claims data, such as cholesterol level, may be calendar time dependent.

Disease Progression After Lateral and Medial Unicondylar Knee Arthroplasty.

BACKGROUND: Medial unicompartmental knee arthroplasty (UKA) has been a successful option for treatment of arthritis in patients with a healthy lateral compartment. However, lateral UKA is less common and results are less consistent. The purpose of this study is to compare progression of radiographically evident osteoarthritis in unoperated compartments during 5 years after lateral and medial UKA. METHODS: We undertook serial radiographic evaluation of 20 lateral and 114 medial UKA performed by the senior author during calendar years 2007-2008. Anteroposterior, lateral, and skyline radiographs obtained preoperatively and 1 and 5+ (mean, 5.3; range, 5.1-6.4) years postoperatively were independently graded for osteoarthritis in the unoperated tibiofemoral (TF) and patellofemoral (PF) compartments using established scales of Kellgren (0-4 point global scale for osteoarthritis), Ahlbäck (0-5 point scale based on joint space narrowing), and Altman (0-12 point composite criteria score). Rates of disease progression were compared between lateral and medial UKA groups using bivariate methods and multilevel growth models that adjusted for baseline characteristics. RESULTS: All mean disease grades for the TF and PF compartments increased (worsened) over time. The adjusted rate of Kellgren grade change was statistically (P < .05) faster for lateral UKA in the TF and PF compartments, as was Ahlbäck change in the TF compartment. Kellgren grade for the TF compartment of lateral and medial UKA groups increased 1.1 vs 0.6 points on average over 5 years adjusted for age, sex, and body mass index (P < .001). CONCLUSION: Surgeons should consider the propensity for faster disease progression after UKA in evaluating patients with isolated lateral compartment disease. LEVEL OF EVIDENCE: Level III, therapeutic study.

Knee strength, power and stair performance of the elderly 5 years after unicompartmental knee arthroplasty.

BACKGROUND: Unicompartmental knee arthroplasty (UKA) has been shown to demonstrate some satisfactory short-term outcomes. However, to our knowledge, there have been no reports on midterm or long-term knee extensor strength and leg extensor power post-UKA. AIMS: Therefore, the purposes of this study were: (1) to assess the isokinetic knee extensor strength, leg extensor power and stair performance of elderly participants at 5 years UKA post-operation; (2) to compare the differences in knee extensor strength and leg extensor power between the UKA and contralateral healthy limbs. METHODS: Nineteen elderly participants (75 ± 5 years) who had a medial or a lateral compartment UKA at 5 years post-operation were recruited. The isokinetic knee extensor strength and leg extensor power were measured. The stair performance was tested on a 4-step stair, and ascent and descent velocities were calculated. The pain level was assessed. RESULTS: The UKA limbs' knee extensor strength and leg extensor power were 1.01 ± 0.39 Nm/kg and 0.98 ± 0.27 W/kg, respectively. The stair ascent and descent velocities were 0.37 ± 0.07 and 0.38 ± 0.11 m/s, respectively. In addition, the UKA limbs exhibited comparable knee strength and leg power relative to the contralateral limbs. DISCUSSION: In general, the knee extensor strength and leg extensor power exhibited by the UKA limbs at 5 years post-operation may be typical in comparison with the normative data. CONCLUSIONS: We suggest that UKA is a satisfactory treatment in regard to the recovery of knee strength, leg power and ability to climb up and down stairs.

Balanced Flexion and Extension Gaps Are Not Always of Equal Size.

BACKGROUND: It has been widely accepted in total knee arthroplasty (TKA) that flexion and extension gaps in the disarticulated knee during surgery should be equalized. We hypothesized that tensioning during assessment of the flexion gap can induce temporary widening of the gap due to posterior tibial translation. We aimed to describe posterior tibial translation at flexion gap (90°) assessments and assess the correlation of tibial translation with laxity (flexion space increase) using constrained and non-constrained inserts. METHODS: Imageless navigation was used to measure flexion angle, tibial position relative to the femoral axis, and lateral/medial laxity in 30 patients undergoing primary TKA. Trialing was conducted using posteriorly stabilized and cruciate retaining trials of the same size to elucidate the association of posterior tibial translation with changes in joint capsule laxity at 90° knee flexion. RESULTS: All patients demonstrated posterior tibial translation during flexion gap assessment relative to their subsequent final implantation [mean ± standard deviation (range), 11.3 ± 4.4 (4-21) mm]. Positive linear correlation [r = 0.69, 95% confidence interval (CI) 0.44-0.84, P ≤ .001] was demonstrated between translations [8.7 ± 2.4 (3-13) mm] and laxity changes [2.9° ± 2.0° (-0.7° to 7.4°)] at 90° of flexion. CONCLUSION: Posterior tibial translation can cause artifactual widening of the flexion gap during gap balancing in posteriorly stabilized TKA, which can be of sufficient magnitude to alter femoral component size selection for some patients. Recognition and management of these intra-operative dynamics for optimal kinematics could be feasible with the advent of robotic applications.

Use of Near-Infrared Spectroscopy to Detect Sustained Hyperaemia Following Lower Extremity Trauma.

INTRODUCTION: Patients who sustain lower extremity trauma are at highest risk for acute compartment syndrome (ACS) during the first 48 hours after surgical stabilization. Near-infrared spectroscopy (NIRS) may be a useful monitoring tool for ACS during this period; however, expected normal values have yet to be established. This study sought to evaluate whether the expected hyperaemic response is present 48 hours postoperatively, using NIRS. MATERIALS AND METHODS: Participants consisted of 25 cases with acute unilateral lower extremity fractures. NIRS measurements for hemoglobin saturated with oxygen (rSO2) were taken approximately 48 hours after surgical stabilization for each compartment bilaterally, using the contralateral (uninjured) leg as an internal control. RESULTS: Mean rSO2 values taken 48 hours from surgical stabilization from each compartment of the patients' injured legs were significantly higher than the mean values of the contralateral legs (injured = 70, 68, 72, 70; contralateral = 55, 54, 57, 56 for anterior, lateral, deep posterior, and superficial posterior compartments, respectively; p < 0.0001 for all compartments). CONCLUSIONS: These results suggest that the hyperaemic response to injury remains present at 48 hours after surgical stabilization, and that NIRS values in an injured extremity should be expected to remain elevated throughout the window of concern for ACS. NIRS may be a valuable tool in monitoring leg injuries during this critical time period.

Knee moments after unicompartmental knee arthroplasty during stair ascent.

BACKGROUND: For unicompartmental knee arthroplasty (UKA), abnormal loading on the tibiofemoral joint could exacerbate knee osteoarthritis or implant wear. Joint moments are an indirect measure of such loading. However, little is known about knee moments of patients with UKA, tempering enthusiasm for its use. QUESTIONS/PURPOSES: In patients with UKAs performing stair ascent, we (1) determined whether interlimb differences for knee moments are demonstrated, (2) described the knee kinetics of patients with medial and lateral UKAs, and (3) investigated possible factors that might influence the knee abductor moments. METHODS: In our cross-sectional study, we recruited 26 patients with UKA with nondiseased contralateral limbs who performed stair ascent. Seventeen patients had medial UKAs and nine had lateral UKAs. Paired t-tests and CIs were applied to determine interlimb differences within each UKA group for peak knee moments and times to peak moments. RESULTS: During stair ascent, the medial UKA group displayed greater peak extensor moments for the nondiseased compared to the UKA limb (p = 0.030), whereas the lateral UKA group did not (p = 0.087). For both medial and lateral UKA groups, the UKA limb demonstrated greater internal peak abductor moments (p = 0.005 and 0.013, respectively). Both UKA groups exhibited knee moments similar to those in the literature. Limb dominance and postoperative time were correlated for both UKA groups. CONCLUSIONS: Reduced knee extensor moments of limbs with UKA displayed by some participants may indicate less compressive loading on the tibiofemoral joint surfaces, whereas the increased abductor moments suggest increased compression on the medial compartment. These findings suggest UKA knees may not be subjected to excessive loads regardless of the side reconstructed.

Can squeaking with ceramic-on-ceramic hip articulations in total hip arthroplasty be avoided?

Squeaking is a recognized complication of total hip arthroplasty with ceramic on ceramic bearings but the etiology has not been well identified. We evaluated 183 hips in 148 patients who had undergone ceramic-on-ceramic noncemented total hip arthroplasties at one center between 1997-2007 by standardized telephone interviews and radiographic review. Audible squeaking was reported from 22 hips (12% of 183) of 19 patients. Prevalence of squeaking was associated with younger age; obesity; lateralized cup position; use of beta titanium alloy femoral components and shortened head length options; and higher reported activity level, greater pain, and decreased satisfaction at the time of the interview. Squeaking was described as having little personal significance by most patients. Squeaking might be preventable in part through medialization of the acetabular cup and avoidance of the use of shortened femoral necks.

Does interlimb knee symmetry exist after unicompartmental knee arthroplasty?

BACKGROUND: Unicompartmental knee arthroplasty (UKA) has long been a treatment option for patients with disease limited primarily to one compartment with small, correctable deformities. However, some surgeons presume that normal kinematics of a lateral compartment UKA are difficult to achieve. Furthermore, it is unclear whether UKA restores normal knee kinematics and interlimb symmetry. QUESTIONS/PURPOSES: We determined knee kinematics exhibited during stair ascent by patients with medial- (MED-UKA) or lateral-UKA (LAT-UKA) and if the knee kinematics of the operated and nonoperated limbs were symmetrical. METHODS: Participants were 17 individuals with MED-UKA and nine with LAT-UKA, all with nondiseased contralateral limbs. For each limb, participants walked up four stairs for five trials while a motion-capture system obtained reflective marker locations. Temporal events were determined by force platform signals. Interlimb symmetry was classified for temporal gait and knee angular kinematics by comparing observed interlimb differences with clinically meaningful differences set at 5% of stride time for temporal variables and 5° for angular variables. The minimum postoperative followup was 6 months (median, 24 months; range, 6-53 months). RESULTS: Neither group demonstrated clinically meaningful mean interlimb differences. However, approximately half of participants of each UKA group displayed asymmetry favoring the operative or nonoperative limb with similar frequency. CONCLUSIONS: Many patients undergoing UKA demonstrate kinematic interlimb symmetry during stair ascent. Interlimb asymmetry may be affected by a variety of factors unrelated to the UKA. CLINICAL RELEVANCE: A MED- or LAT-UKA can potentially restore normal knee function for a demanding task of daily life.

Relationship between near infrared spectroscopy and intra-compartmental pressures.

BACKGROUND: Near infrared spectroscopy (NIRS) has been suggested as a possible means for detecting perfusion deficits in patients with acute compartment syndrome (ACS). STUDY OBJECTIVES: To longitudinally examine NIRS in an ACS model to determine its responsiveness to decreasing perfusion pressure. METHODS: A NIRS sensor pad was placed under a tourniquet over the anterior compartment in the mid-tibia region on 20 volunteers. Initial perfusion pressures and NIRS values were recorded. The tourniquet pressure was sequentially raised by 10 mm Hg in 10-min intervals until systolic pressure was surpassed. NIRS values and perfusion pressure were determined at the end of each 10-min interval. RESULTS: There was no change in mean NIRS values from the initial baseline until 30 mm Hg of perfusion pressure was reached. Additionally, a statistically significant drop in mean NIRS values was observed as perfusion pressures dropped from 10 mm Hg to 0 mm Hg, and again with subsequent decreases of 10 mm Hg perfusion pressure until systolic pressure was surpassed. CONCLUSIONS: These results coincide with previously published studies using alternative methods of measuring blood flow or perfusion. NIRS values were responsive to decreasing perfusion pressures over a longitudinal period of time in an ACS model. These results suggest that NIRS may be useful for continuous, non-invasive monitoring of patients for whom ACS is a concern. Additional studies on traumatized patients are required.

The John Insall Award: no functional advantage of a mobile bearing posterior stabilized TKA.

BACKGROUND: Mobile bearing (MB) total knee design has been advocated as a means to enhance the functional characteristics and decrease the wear rates of condylar total knee arthroplasty (TKA). However, it is unclear if these designs achieve these goals. QUESTIONS/PURPOSES: We asked whether function of patients or survivorship would be greater or complications would be lesser in groups of patients with MB compared with fixed bearing (FB) TKA. We also sought to describe retrieval findings. METHODS: We randomized 507 primary TKAs in 416 eligible patients to receive MB (n = 252) or FB (n = 255) devices from November 2001 to August 2007 (Investigational Device Exemption G000180, ClinicalTrials.gov registration number NCT00946075). Patients were blinded to treatment allocation. WOMAC Index, SF-12 Health Survey, knee range of motion, and Knee Society scores were collected and compared preoperatively and at 6, 12, and 24 months postoperatively. We recorded device failures and complications until October 2009. Kaplan-Meier survivorship was compared using the log rank test. Twelve retrieved MB devices underwent pathologic analysis. The minimum postoperative time was 2.2 years (mean, 5.9 years; range, 2.2-7.9 years). RESULTS: We found no differences in mean clinical assessment scores or mean score changes from baseline at any postoperative interval through 2 postoperative years. Nineteen of the 252 MB and 13 of the 255 FB knees had undergone revision of any component. Estimated survival at 6 postoperative years was similar for the two devices: 90.1% (95% confidence interval [CI], 84.1-93.9) for MB and 94.2% (95% CI, 90.1-96.6) for FB. Two MB and no FB tibial components were revised for loosening. There was one case of MB insert dislocation. Retrieved MB devices demonstrated no unexpected wear or mechanical device failures. CONCLUSION: We found no evidence of functional advantage of the MB design. Survivorship was similar, although the study is limited by short duration of followup.