An advanced knee simulator model can reproducibly be used for ligament balancing training during Total Knee Arthroplasty.

Introduction A critical and difficult aspect of total knee arthroplasty (TKA) is ligamentous balancing for which cadavers and models have played a large role in the education and training of new arthroplasty surgeons, though they both have several shortcomings including cost, scarcity, and dissimilarity to in vivo ligament properties. An advanced knee simulator (AKS) model based on computed tomography (CT) scans was developed in the setting of these challenges with cadavers and previous models. In this study, we compared the ligament balancing between AKS and human cadaveric knees to assess the validity of using the AKS for ligament balancing training during TKA. Methods A CT scan of a TKA patient with varus deformity was used to design the AKS model with modular components, using three-dimensional (3D) printing. Three fellowship-trained arthroplasty surgeons used technology-assisted TKA procedure to plan and balance three cadaver knees and the AKS model. Medial and lateral laxity data were captured using manual varus and valgus stress assessments for cadavers and the model in an extension pose (10 ̊ of flexion from terminal extension) and between 90 and 95 degrees for flexion. After pre-resection assessments, surgeons planned a balanced cruciate-retaining TKA. Following bony cuts and trialing, extension and flexion ligament laxity values were recorded in a similar manner. Descriptive statistics and student t-tests were performed to compare the cadavers and model with a p-value set at 0.05. Results Pre-resection medial/lateral laxity data for both extension and flexion were plotted and showed that the highest standard deviation (SD) for the cadavers was 0.67 millimeters, while the highest SD for the AKS was 1.25 millimeters. A similar plot for trialing demonstrated that the highest SD for the cadavers was 0.6 millimeters, while the highest SD for the AKS was 0.61 millimeters Discussion The AKS trialing data was highly reproducible when compared to cadaveric data, demonstrating the value of the AKS model as a tool to teach ligament balancing for TKA and for future research endeavors.

2019 Mark Coventry Award: A multicentre randomized clinical trial of tranexamic acid in revision total knee arthroplasty: does the dosing regimen matter?.

AIMS: Tranexamic acid (TXA) is proven to reduce blood loss following total knee arthroplasty (TKA), but there are limited data on the impact of similar dosing regimens in revision TKA. The purpose of this multicentre randomized clinical trial was to determine the optimal regimen to maximize the blood-sparing properties of TXA in revision TKA. PATIENTS AND METHODS: From six-centres, 233 revision TKAs were randomized to one of four regimens: 1 g of intravenous (IV) TXA given prior to the skin incision, a double-dose regimen of 1 g IV TXA given both prior to skin incision and at time of wound closure, a combination of 1 g IV TXA given prior to skin incision and 1 g of intraoperative topical TXA, or three doses of 1950 mg oral TXA given two hours preoperatively, six hours postoperatively, and on the morning of postoperative day one. Randomization was performed based on the type of revision procedure to ensure equivalent distribution among groups. Power analysis determined that 40 patients per group were necessary to identify a 1 g/dl difference in the reduction of haemoglobin postoperatively between groups with an alpha of 0.05 and power of 0.80. Per-protocol analysis involved regression analysis and two one-sided t-tests for equivalence. RESULTS: In total, one patient withdrew, five did not undergo surgery, 16 were screening failures, and 25 did not receive the assigned treatment, leaving 186 patients for analysis. There was no significant difference in haemoglobin reduction among treatments (2.8 g/dl for single-dose IV TXA, 2.6 g/dl for double-dose IV TXA, 2.6 g/dl for combined IV/topical TXA, 2.9 g/dl for oral TXA; p = 0.38). Similarly, calculated blood loss (p = 0.65) and transfusion rates (p = 0.95) were not significantly different between groups. Equivalence testing assuming a 1 g/dl difference in haemoglobin change as clinically relevant showed that all possible pairings were statistically equivalent. CONCLUSION: Despite the higher risk of blood loss in revision TKA, all TXA regimens tested had equivalent blood-sparing properties. Surgeons should consider using the lowest effective dose and least costly TXA regimen in revision TKA. Cite this article: Bone Joint J 2019;101-B(Supple 7):10-16.

2019 John Insall Award: Fructosamine is a better glycaemic marker compared with glycated haemoglobin (HbA1C) in predicting adverse outcomes following total knee arthroplasty: a prospective multicentre study.

AIMS: The best marker for assessing glycaemic control prior to total knee arthroplasty (TKA) remains unknown. The purpose of this study was to assess the utility of fructosamine compared with glycated haemoglobin (HbA1c) in predicting early complications following TKA, and to determine the threshold above which the risk of complications increased markedly. PATIENTS AND METHODS: This prospective multi-institutional study evaluated primary TKA patients from four academic institutions. Patients (both diabetics and non-diabetics) were assessed using fructosamine and HbA1c levels within 30 days of surgery. Complications were assessed for 12 weeks from surgery and included prosthetic joint infection (PJI), wound complication, re-admission, re-operation, and death. The Youden's index was used to determine the cut-off for fructosamine and HbA1c associated with complications. Two additional cut-offs for HbA1c were examined: 7% and 7.5% and compared with fructosamine as a predictor for complications. RESULTS: Overall, 1119 patients (441 men, 678 women) were included in the study. Fructosamine level of 293 µmol/l was identified as the optimal cut-off associated with complications. Patients with high fructosamine (> 293 µmol/l) were 11.2 times more likely to develop PJI compared with patients with low fructosamine (p = 0.001). Re-admission and re-operation rates were 4.2 and 4.5 times higher in patients with fructosamine above the threshold (p = 0.005 and p = 0.019, respectively). One patient (1.7%) from the elevated fructosamine group died compared with one patient (0.1%) in the normal fructosamine group (p = 0.10). These complications remained statistically significant in multiple regression analysis. Unlike fructosamine, all three cut-offs for HbA1c failed to show a significant association with complications. CONCLUSION: Fructosamine is a valid and an excellent predictor of complications following TKA. It better reflects the glycaemic control, has greater predictive power for adverse events, and responds quicker to treatment compared with HbA1c. These findings support the screening of all patients undergoing TKA using fructosamine and in those with a level above 293 µmol/l, the risk of surgery should be carefully weighed against its benefit. Cite this article: Bone Joint J 2019;101-B(7 Supple C):3-9.

Impacted morselized cancellous bone: mechanical effects of defatting and augmentation with fine hydroxyapatite particles.

Geotechnical engineering testing techniques were used to study the mechanical properties of morselized cancellous bone (MCB) and the effects of defatting and augmentation with fine hydroxyapatite (HA) particles. Bovine and human cancellous bone was morselized, rinsed, and manually squeezed to remove excess fluid, producing a standard surgical MCB sample that was also used as a control. Some of the MCB was defatted with heat and detergent and mixed with HA particles in ratios ranging from 0% to 100% HA. Compaction tests were used to determine the effects of moisture content and the amount of MCB that can be packed into a confined space. One-dimensional consolidation tests were used to determine the uniaxial strain behavior, confined modulus, and steady-state creep rate. The compaction tests demonstrated that defatting and adding HA particles significantly increased density. The one-dimensional consolidation tests showed that strain was decreased, modulus was increased and the creep rate was decreased by defatting and adding HA.

Accuracy of computer assisted percutaneous placement of iliosacral screws: a cadaveric study.

OBJECTIVE: To determine the accuracy of computer-assisted fluoronavigation for percutaneous iliosacral screw placement. MATERIALS AND METHODS: A fluoronavigation system (Stryker Navigation System, Stryker Leibinger, Kalamazoo, MI) was used to guide the placement of four iliosacral screws into the S-1 bodies of each of five cadaveric pelvic specimens with intact soft tissues. Accuracy of screw placement was verified by radiographs, CT scans, and direct dissection. RESULTS: All 20 screws were placed accurately without complications. Nineteen screws were completely contained within the osseous "safe zone." On direct dissection, one screw was noted to have penetrated the S-1 foramina by 3 mm without impingement on the nerve root. This was not detected on radiograph or CT scan. CONCLUSION: The results of this study support the safety and accuracy of computer-assisted fluoronavigation for iliosacral screw placement. The advantages include decreased fluoroscopic time, real-time simultaneous visualization of all three views (inlet, outlet, and lateral), and increased accuracy of placement. Clinical study is warranted.

Endogenous norepinephrine regulates blood flow to the intact rat tibia.

The goal of our study was to determine if endogenous norepinephrine (NE) has a role in the regulation of basal blood flow to intact bone. The experimental plan was to measure bone blood flow before and after pharmacological blockade of alpha-adrenergic receptors. A significant increase in blood flow after receptor blockade would suggest that endogenous norepinephrine exerts a tonic constrictor effect on the vessels supplying blood to the bone. Mature, male rats were anesthetized with Inactin. Arterial blood pressure and left tibia blood flow (laser Doppler flowmetry) were measured. A cannula was inserted into the right iliac artery and advanced to the aortic bifurcation to deliver drugs into the left hindlimb circulation, including the left tibia vasculature. Bolus injection of norepinephrine caused a dose-dependent decrease in bone blood flow (30-40%). Blockade of alpha-adrenergic receptors with phentolamine or phenoxybenzamine attenuated by more than 50% the norepinephrine-induced decrease in bone blood flow. In separate rats that had not received exogenous norepinephrine, injection of phentolamine alone decreased bone vascular resistance by 34+/-3%. Similarly, phenoxybenzamine decreased resistance by 25+/-4%. These results are consistent with the conclusion that alpha-adrenergic receptors mediate a significant constriction of blood vessels which participate in the partial control of basal blood flow to the intact rat tibia.

Increased peak contact stress after incongruent reduction of transverse acetabular fractures: a cadaveric model.

BACKGROUND: The objective of this study was to determine the peak contact pressure with varying degrees of articular cartilage step-off in a transtectal acetabular fracture model. METHODS: Five fresh frozen cadaveric hip joints were potted in a custom loading fixture. The five specimens were then tested at loads of 445 N (newton) (100 lb) and 1,335 N (300 lb) intact and after a transverse osteotomy at step-off levels from 0 to 5 mm in 1-mm increments. RESULTS: Articular cartilage step-off of greater than 1 mm led to significantly increased contact stress at the loaded acetabular articular surface. Mean peak pressure measured at 1,335 N of loading in all intact specimens before the osteotomy was approximately 10 MPa. Peak pressure after a transverse acetabular fracture did not change when the fracture was perfectly reduced. At 1 mm of step-off, the peak pressure increased by approximately 20% but was not statistically significant. With step-off of > 2 mm or greater, the peak pressure increase was approximately 50% and was statistically significant. CONCLUSION: On the basis of our study, transverse acetabular fractures with greater than 1 mm of displacement can lead to significant increase in peak pressure at the articular surface.

Bone blood flow and vascular reactivity.

Blood flow is essential for normal bone growth and bone repair. Like other organs, the regulation of blood flow to bone is complex and involves numerous physiologic mechanisms including the sympathetic nervous system, circulating hormones, and local metabolic factors. Our studies addressed the following questions: (1) Which endogenous vasoconstrictor agents regulate in vivo blood flow to bone? (2) Does a decrease in bone vascular reactivity to vasoconstrictor hormones account for the increase in blood flow during bone healing? (3) Does the endothelium influence bone arteriolar function? An intact bone model was developed in the rat to assess hormonal regulation of in vivo bone blood flow and in vivo bone vascular reactivity. An isolated, perfused bone arteriole preparation was employed to characterize the responsiveness of small resistance-size arterioles (diameter < 100 microm) to vasoconstrictor hormones and to evaluate the role of the vascular endothelium to modulate vascular smooth muscle reactivity. Our results indicate that: (1) though exogenous endothelin is a potent constrictor of the in vivo bone vasculature, endogenous endothelin does not actively regulate in vivo blood flow; (2) the increase in blood flow to a bone injury site is not due to a decrease in bone vascular sensitivity to norepinephrine, and (3) isolated bone arterioles of young rats are very sensitive to vasoconstrictor hormones but exhibit only modest endothelium-mediated vasodilation.

Mechanical properties of compacted morselized cancellous bone graft using one-dimensional consolidation testing.

Failures of orthopaedic procedures that use morselized cancellous bone (MCB) graft for load bearing are often due to gross displacement within the graft material. For this reason the mechanical behavior of MCB must be better understood. Our purpose is to present a detailed testing methodology for the mechanical characterization of MCB, and to illustrate how this methodology can be used to study the influence of water and fat content. Complete one-dimensional consolidation testing was performed on bovine cancellous bone processed to represent MCB typically used in surgery (52% water, 31% fat). The one-dimensional consolidation strain under a stress of 1.09MPa was 30.9% and the confined modulus was 8.0MPa. The coefficient of consolidation (rate of consolidation) was 2. 2x10(-5)cm(2)/s and the coefficient of secondary strain (steady-state creep rate) was 1.9%. While reducing the water content alone had some influence on properties, reducing the fat content improved both the static and dynamic behavior. A sample of MCB which had fat intentionally minimized and a lower overall moisture content (56% water, 5% fat) demonstrated 23.1% strain, a confined modulus of 9.6MPa, a coefficient of consolidation of 3.4x10(-3)cm(2)/s, and a coefficient of secondary strain of 0.9%. The test methods described in this technical note can be used to evaluate the influence of fluid content on the mechanical behavior of MCB.

Cross-sectional geometry of the sacral ala for safe insertion of iliosacral lag screws: a computed tomography model.

OBJECTIVE: To measure the dimensions of the narrowest portion of the sacral ala for safe insertion of iliosacral lag screws. DESIGN: Computed tomography (CT) model. SETTING: Level One trauma center. PATIENTS: Thirteen adult patients underwent pelvic CT imaging. MAIN OUTCOME MEASURE: Axial CT scans of intact pelves were reformatted in the sagittal plane at three-millimeter intervals from the first sacral body (S1 body) to the sacroiliac (SI) joint. Computer analysis and measurements of sacral geometry were used to determine the narrowest portion of the bony sacral ala. The maximum height, maximum width, and slope of the sacral ala through its geometric center in cross-section were measured. RESULTS: The narrowest portion of the sacral ala in all patients was consistently located at the junction between the sacral body and the alar wings, termed the sacral pedicle, directly cephalad to the first sacral foramen. The average slope of the sacral ala at the sacral pedicle was 45.08 degrees (range 25 to 65 degrees). The average maximum height at the geometric center in cross-section was 27.76 millimeters, and the average width was 28.05 millimeters. However, outside the geometric center there was a sharp decrease in height and width of the sacral ala that was in large part determined by its relative slope. CONCLUSION: Although the cross-sectional geometry of the sacral ala is highly variable among patients, there is ample space for iliosacral screws. To ensure safe insertion, iliosacral lag screws must be positioned in the geometric center of the sacral ala to avoid extraosseous placement.

Mood during epidural patient-controlled analgesia with morphine or fentanyl.

BACKGROUND: Mood states during epidural opioids are not known. The authors studied the change in mood during the 48-h period of epidural morphine and epidural fentanyl in 47 patients after elective hip or knee joint arthroplasty. METHODS: An epidural catheter was inserted at the L2-L3 or L3-L4 interspace. Anesthesia was induced with thiopenthal and maintained with isoflurane and nitrous oxide. One hour before the conclusion of the operation, patients received an epidural bolus injection of 2 mg morphine (n = 23) or 100 microg fentanyl (n = 24), followed by the same opiate (125 microg/ml morphine or 25 microg/ml fentanyl) epidurally delivered by a patient-controlled analgesia (PCA) pump in the postoperative period for 48 h. Mood was assessed using the bipolar form of the Profile of Mood States before operation and 24 h, 48 h, and 72 h after operation. RESULTS: There was no significant difference in pain intensity between the groups during epidural PCA. Mood states became more positive over time in the patients who received morphine (P < 0.01 at 48 h) and negative in those who were given fentanyl (P < 0.01 at 24 and 48 h, respectively) compared with those before the operation, and they were more positive in the morphine than in the fentanyl group at 24 h, 48 h (P < 0.05), and 72 h (P < 0.01). Patients in the morphine group were more composed, agreeable, elated, confident, energetic, and clearheaded than were those in the fentanyl group (P < 0.05). There was no correlation between mood scores and pain scores in either group. There was an inverse correlation at 48 h between mood scores and plasma fentanyl concentrations (r = -0.58, P < 0.05). CONCLUSION: Mood states are significantly more positive during epidural morphine PCA than they are during epidural fentanyl PCA.

Arthroplasty in the goat hip.

The goat is a reliable and practical animal model for study of the hip. The authors describe a safe and effective operative approach to the goat hip.

Intraoperative monitoring of motor pathways during operative fixation of acute acetabular fractures.

OBJECTIVE: To determine whether intra-operative spontaneous electromyography (EMG) was superior to somatosensory evoked potentials (SSEP) in the prevention of iatrogenic sciatic nerve injury. DESIGN: Prospective, consecutive. SETTING: Tertiary referral, teaching Hospital in New York City. PATIENTS: Seventy-four patients with acutely displaced acetabular fractures. MAIN OUTCOME MEASURE: Group A consisted of 24 patients who underwent intraoperative sciatic nerve monitoring using SSEP only. Group B consisted of 50 patients who underwent monitoring using both SSEP and spontaneous EMG. Motor potentials were recorded from the tibialis anterior, peroneus longus, abductor hallucis, and flexor hallucis longus muscles. All patients had independent preoperative and postoperative evaluations by the same neurologist. RESULTS: One iatrogenic sciatic nerve injury occurred in group A and none in group B. Prolonged sciatic nerve compromise, demonstrated by significant intraoperative SSEP changes, occurred 2.4 times per case in group A and only 0.8 times per case in group B. In group B, spontaneous EMG noted compromise an average of 3.6 times per case (p < 0.0001). CONCLUSIONS: The results of this study support spontaneous EMG as feasible and superior to SSEP monitoring in detecting intraoperative sciatic nerve comprise in acute acetabular fracture surgery. Spontaneous EMG permits earlier detection of intraoperative sciatic nerve comprise, allowing a more rapid response of the surgical team to noxious nerve stimuli. This may prevent permanent neurologic sequellae.

Femoral component revision using impacted morsellised cancellous graft. A biomechanical study of implant stability.

We have tested the axial and torsional stability of femoral components after revision arthroplasty in a cadaver model, using impacted morsellised cancellous graft and cement. Each one of six matched pairs of fresh frozen human femora had either a primary or a revision prosthesis cemented in place. For the 'revision' experiments, all cancellous bone was removed from the proximal femur which was then over-reamed to create a smooth-walled cortical shell. An MTS servohydraulic test frame was used to apply axial and torsional loads to each specimen through the prosthetic femoral heads with the femur submerged in isotonic saline solution at 37 degrees C. The mean subsidence was 0.27 +/- 0.17 mm for the primary and 0.52 +/- 0.30 mm for the revision groups. The difference was statistically significant (p < 0.025), but the mean subsidence was <1 mm in both groups. The mean maximum torque before failure was 42.9 +/- 26.9 N-m for the primary and 34.8 +/- 20.7 N-m for the revision groups. This difference was not statistically significant (p > 0.015). Based on our results we suggest that revision of the femoral component using morsellised cancellous graft followed by cementing with a collarless prosthesis with a polished tapered stem restores the integrity of the proximal femur and provides immediate stability of the implant.

Femoral component revision using an uncemented, proximally coated, long-stem prosthesis.

Sixty-nine femoral component revisions with uncemented, metaphyseal-filling, proximally coated, chrome-cobalt, long-stem, curved prostheses were retrospectively reviewed 2 to 5 years after operation. The mean age of the patients was 62 years. The mean clinical follow-up period was 3 years, and the mean radiographic follow-up period was 2.8 years. Sixty-two hips underwent revision secondary to aseptic loosening after previous cemented total hip arthroplasty. Average preoperative Harris hip score was 51 points, which improved to 82 points. Complications included an intraoperative fracture in 45.9%. Repeat revision or component removal had been necessary in 6 patients (8.7%). An additional 14 patients (20%) had pain and radiographic evidence of subsidence. Overall 5-year survivorship free of moderate pain or revision was 82% for the entire group, but was 58% for the fracture subgroup at 4 years.

Long-term results of proximal femoral replacement for non-neoplastic disorders.

We reviewed retrospectively 50 consecutive total hip arthroplasties with proximal femoral replacement prostheses in 49 patients. All the patients had massive bone loss. There were 31 women and 18 men who had undergone a mean of 3.1 hip operations. At the last review, 15 patients had died and two had been lost to follow-up, so that 32 patients (33 hips) were available for assessment. The mean age of the patients at the time of the operation was 60.6 years. The mean length of clinical follow-up was 11.1 +/- 4 years, and mean radiographic follow-up was 7.6 +/- 3.2 years. The average preoperative Harris hip score was 46 +/- 13 points, which improved to 80 +/- 10 points after one year and to 76 +/- 16 points at the latest follow-up. The most frequent complication was dislocation, which occurred in 11 hips. Four femoral components and seven acetabular prostheses were revised because of aseptic loosening. With revision at the end point, survivorship after total hip arthroplasty with a proximal femoral replacement prosthesis was predicted to be 64% at 12 years. Although our preliminary results of hip salvage with a proximal femoral replacement prosthesis were encouraging, a longer follow-up has shown a higher rate of failure.

Total knee arthroplasty with the kinematic condylar prosthesis. A ten-year follow-up study.

Of 168 consecutive knees (118 patients) that had been treated with an arthroplasty with use of a kinematic total condylar prosthesis that allowed retention of the posterior cruciate ligament, 119 knees (eighty-four patients) were available for review at a mean of 10.0 +/- 0.7 years after the operation. The Hospital for Special Surgery knee score improved significantly, from a mean of 55 +/- 12 points preoperatively to a mean of 81 +/- 9 points at ten years (p < 0.0001). Radiolucent lines about the patellar component, present in thirty-five of eighty-three knees at the latest follow-up examination, were related to malpositioning of the tibial and femoral components. Six revisions were performed, and four of them were for a loose patellar component. The rate of deep infection was 1 per cent (one knee). Complications occurred in twenty-six knees (22 per cent). With revision as the end point, the rate of survival of the prostheses was estimated to be 96 per cent at ten years. The knee scores, the rate of survival of the implants, and the range of motion of the knees in the current study were similar to those reported previously for patients who had insertion of a total condylar prosthesis with sacrifice of the posterior cruciate ligament and for those who had substitution of the posterior cruciate ligament with a posterior stabilized prosthesis. A prosthesis that has a metal-backed tibial component and that allows preservation of the posterior cruciate ligament provides durable results, but loosening of the patellar component remains a major problem.

Custom-made segmental femoral replacement prosthesis in revision total hip arthroplasty.

Patients who present with failed total hip arthroplasty and significant proximal femoral bone loss pose a challenging reconstructive problem. When the integrity of the host proximal femur can be salvaged with cortical strut grafts, conventional long-stem femoral components can be used. If there is massive proximal femoral bone loss, hip salvage can be accomplished with a proximal femoral replacement prosthesis or an allograft-prosthesis composite. Although our early results with a proximal femoral replacement prosthesis were good, long-term results reveal a high rate of dislocation and acetabular component loosening, with an overall survivorship of 73% at 11 years. We have, therefore, limited the use of a proximal femoral replacement prosthesis to the elderly and inactive patient. We are encouraged by the preliminary results of total hip arthroplasty with a second-generation, modular, porous-coated, proximal femoral replacement prosthesis. Longer follow-up is required to determine whether these design modifications improve the results of this type of reconstructive procedure in revision total hip arthroplasty.