Surgeons commonly resect additional distal femur during primary total knee arthroplasty (TKA) to correct a flexion contracture to restore range of motion and knee function. However, the effect of joint line elevation on the resulting TKA kinematics including frontal plane laxity is unclear. Thus, our goal was to quantify the effect of additional distal femoral resection on passive extension and mid-flexion laxity. Six computational knee models with capsular and collateral ligament properties specific to TKA were developed and implanted with a contemporary posterior-stabilized TKA. A 10° flexion contracture was modeled by imposing capsular contracture as determined by simulating a common clinical exam of knee extension and accounting for the length and weight of each limb segment from which the models were derived (Figure 1). Distal femoral resections of 2 mm and 4 mm were simulated for each model. The knees were then extended by applying the measured knee moments to quantify the amount of knee extension. The output data were compared with a previous cadaveric study using a two-sample two-tailed t-test (p<0.05) [1]. Subsequently, varus and valgus torques of ±10 Nm were applied as the knee was flexed from 0° to 90° at the baseline, and after distal resections of 2 mm, and 4 mm. Coronal laxity, defined as the sum of varus and valgus angulation in response to the applied varus and valgus torques, was measured at 30° and 45°of flexion, and the flexion angle was identified where the increase in laxity was the greatest with respect to baseline.Introduction
Methods
In total knee arthroplasty (TKA), tibial insert thickness is determined intraoperatively by applying forces that generate varus-valgus moments at the knee and estimating the resulting gaps. However, how the magnitude of applied moments and the surgeon's perception of gaps affect the thickness selection is unclear. We determined this relationship using an in vitro human cadaveric model. Six pelvis-to-toe specimens (72±6 years old, four females) were implanted by an expert surgeon with a PS TKA using measured resection. Pliable sensors were wrapped around medial and lateral aspects of the foot and ankle to measure the applied forces. The forces were scaled by limb length to obtain the moments generated at the knee. Six surgeons with different experience levels independently assessed balance by applying moments in extension and 90° of flexion and choosing the insert they believed fit each knee. Peak moments and the accompanying extension and flexion gap openings as perceived by surgeons were recorded. The two measures were then related to insert choice using a generalized estimating equation.Introduction
Methods
Surgeons commonly resect additional distal femur during primary total knee arthroplasty (TKA) to correct a flexion contracture. However, the effect of joint line proximalization on TKA kinematics is unclear. Thus, our goal was to quantify the effect of additional distal femoral resection on knee extension and mid-flexion laxity. Six computational knee models with TKA-specific capsular and collateral ligament properties were implanted with a contemporary posterior-stabilized TKA. A 10° flexion contracture was modeled to simulate a capsular contracture. Distal femoral resections of +2 mm and +4 mm were simulated for each model. The knees were then extended under standardized torque to quantify additional knee extension achieved. Subsequently, varus and valgus torques of ±10 Nm were applied as the knee was flexed from 0° to 90° at the baseline, +2 mm, and +4 mm distal resections. Coronal laxity, defined as the sum of varus and valgus angulation with respective torques, was measured at mid-flexion.Introduction
Methods
Previous authors have suggested that the analgesic effects of intra-articular morphine may be beneficial. Clonidine has been found to potentiate the analgesic effect of morphine. Following knee arthroscopy, morphine has demonstrated equivocal effect in comparison to bupivicaine for analgesia while circumventing the issue of chondrotoxicity. There have been no studies evaluating the effect of intra-articular morphine following hip arthroscopy. The purpose of this study was to evaluate the efficacy of intra-articular morphine in combination with clonidine on pain and narcotic consumption following hip arthroscopy surgery for femoroacetabular impingement. A retrospective review was performed on 43 patients that underwent hip arthroscopy between September 2014 and May 2015 at our institution for femoroacetabular impingement. All patients received preoperative Celebrex and Tylenol per our anesthesia protocol, and 22 patients received an additional intra-articular injection of 10 mg morphine and 100 mcg of clonidine at the conclusion of the procedure. Narcotic consumption, duration of anesthesia recovery, and perioperative pain scores were compared between the two groups. We found that patients who received intra-articular morphine and clonidine used significantly less opioid analgesic in the PACU, with 23 mEq of morphine equivalents required in the intra-articular morphine and clonidine group compared to 40 mEq of opiod equivalents in the non-injection group (p=0.0259). There were no statistically significant differences in time spent in recovery prior to discharge or in VAS pain scores recorded immediately post-operatively and at one hour following surgery. In conclusion, we found that an intraoperative intra-articular injection of morphine and clonidine significantly reduced the amount of narcotic requirement following hip arthroscopy. We do believe that there may be significant benefits to this, including less systemic effects from overall narcotic usage in the perioperative period. Our study demonstrated a beneficial effect of intra-articular morphine that may help with overall pain improvement, less narcotic consumption, and improved patient satisfaction following outpatient hip arthroscopy. This study provides the foundation for future research currently being conducted in a randomised-control setting.
