Faculty Bibliography

BACKGROUND: Lumbar-pelvic fusion reduces the variation in pelvic tilt in functional situations by reducing lumbar spine flexibility, which is thought to be important in maintaining stability of a total hip arthroplasty (THA). We compared dislocation and revision rates for patients with lumbar fusion and subsequent THA to a matched comparison cohort with hip and spine degenerative changes undergoing only THA. METHODS: We identified patients in New York State who underwent primary elective lumbar fusion for degenerative disc disease pathology and subsequent THA between January 2005 and December 2012. A propensity score match was performed to compare 934 patients with prior lumbar fusion to 934 patients with only THA according to age, gender, race, Deyo comorbidity score, year of surgery, and surgeon volume. Revision and dislocation rates were assessed at 3, 6, and 12 months post-THA. RESULTS: At 12 months, patients with prior lumbar fusion had significantly increased rates of THA dislocation (control: 0.4%; fusion: 3.0%; P < .001) and revision (control: 0.9%; fusion: 3.9%; P < .001). At 12 months, fusion patients were 7.19 times more likely to dislocate their THA (P < .001) and 4.64 times more likely to undergo revision (P < .001). CONCLUSION: Patients undergoing lumbar fusion and subsequent THA have significantly higher risks of dislocation and revision of their hip arthroplasty than a matched cohort of patients with similar hip and spine pathology but only undergoing THA. During preoperative consultation for patients with prior lumbar fusion, orthopedic surgeons must educate the patient and family about the increased risk of dislocation and revision.

BACKGROUND: Valgus cut angle (VCA), defined as the angle between the anatomical and the mechanical axes of femur, is an important parameter upon which a critical step of knee arthroplasty is based. Some variables have been proposed to affect the magnitude of this cut. However, little information is available regarding whether a generic value can be used, or if a patient-specific value from a long leg X-ray, or factors that can be determined preoperatively, is necessary to accurately set the VCA. METHODS: Standard standing 3-joint views were used to measure a number of anatomical measurements in 358 limbs, 202 patients (116 women, 86 men). Neck-shaft angle, medial offset, femoral length (FL), distal femoral articular angle, and VCA were measured. Demographic data including gender and height were extracted from hospital charts. The correlation of VCA with each of the other factors was evaluated using linear regression and t-test and finally multivariate analysis. RESULTS: The average VCA was 5.76 degrees (range 4-8). Gender and distal femoral articular angle were not related to VCA (P = .343 and .995). FL was found to be a function of height with similar effects on multivariate analysis. Only the height (or FL) and femoral offset were identified as independent factors, with a negative correlation for the former (P < .001) and a positive correlation for the latter (P < .001). CONCLUSION: Femoral offset and height are the 2 independent factors determining VCA. Other parameters are indirectly related to these 2 factors. Tall patients with a small femoral offset have smaller VCA and short patients with a large offset have larger VCA. The wide variety of VCA values does not support using a generic value for all patients during knee arthroplasty.

AIMS: Lumbar fusion is known to reduce the variation in pelvic tilt between standing and sitting. A flexible lumbo-pelvic unit increases the stability of total hip arthroplasty (THA) when seated by increasing anterior clearance and acetabular anteversion, thereby preventing impingement of the prosthesis. Lumbar fusion may eliminate this protective pelvic movement. The effect of lumbar fusion on the stability of total hip arthroplasty has not previously been investigated. PATIENTS AND METHODS: The Medicare database was searched for patients who had undergone THA and spinal fusion between 2005 and 2012. PearlDiver software was used to query the database by the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) procedural code for primary THA and lumbar spinal fusion. Patients who had undergone both lumbar fusion and THA were then divided into three groups: 1 to 2 levels, 3 to 7 levels and 8+ levels of fusion. The rate of dislocation in each group was established using ICD-9-CM codes. Patients who underwent THA without spinal fusion were used as a control group. Statistical significant difference between groups was tested using the chi-squared test, and significance set at p < 0.05. RESULTS: At one-year follow-up, 14 747 patients were found to have had a THA after lumbar spinal fusion (12 079 1 to 2 levels, 2594 3 to 7 levels, 74 8+ levels). The control group consisted of 839 004 patients. The dislocation rate in the control group was 1.55%. A higher rate of dislocation was found in patients with a spinal fusion of 1 to 2 levels (2.96%, p < 0.0001) and 3 to 7 levels (4.12%, p < 0.0001). Patients with 3 to 7 levels of fusion had a higher rate of dislocation than patients with 1 to 2 levels of fusion (odds ratio (OR) = 1.60, p < 0.0001). When groups were matched for age and gender to the unfused cohort, patients with 1 to 2 levels of fusion had an OR of 1.93 (95% confidence interval (CI) 1.42 to 2.32, p < 0.001), and those with 3 to 7 levels of fusion an OR of 2.77 (CI 2.04 to 4.80, p < 0.001) for dislocation. CONCLUSION: Patients with a previous history of lumbar spinal fusion have a significantly higher rate of dislocation of their THA than age- and gender-matched patients without a lumbar spinal fusion. Cite this article: Bone Joint J 2017;99-B:585-91.

AIM: To investigate whether normal thickness cartilage in osteoarthritic knees demonstrate depletion of proteoglycan or collagen content compared to healthy knees. METHODS: Magnetic resonance (MR) images were acquired from 5 subjects scheduled for total knee arthroplasty (TKA) (mean age 70 years) and 20 young healthy control subjects without knee pain (mean age 28.9 years). MR images of T1rho mapping, T2 mapping, and fat suppressed proton-density weighted sequences were obtained. Following TKA each condyle was divided into 4 parts (distal medial, posterior medial, distal lateral, posterior lateral) for cartilage analysis. Twenty specimens (bone and cartilage blocks) were examined. For each joint, the degree and extent of cartilage destruction was determined using the Osteoarthritis Research Society International cartilage histopathology assessment system. In magnetic resonance imaging (MRI) analysis, 2 readers performed cartilage segmentation for T1rho/T2 values and cartilage thickness measurement. RESULTS: Eleven areas in MRI including normal or near normal cartilage thickness were selected. The corresponding histopathological sections demonstrated mild to moderate osteoarthritis (OA). There was no significant difference in cartilage thickness in MRI between control and advanced OA samples [medial distal condyle, P = 0.461; medial posterior condyle (MPC), P = 0.352; lateral distal condyle, P = 0.654; lateral posterior condyle, P = 0.550], suggesting arthritic specimens were morphologically similar to normal or early staged degenerative cartilage. Cartilage T2 and T1rho values from the MPC were significantly higher among the patients with advanced OA (P = 0.043). For remaining condylar samples there was no statistical difference in T2 and T1rho values between cases and controls but there was a trend towards higher values in advanced OA patients. CONCLUSION: Though cartilage is morphologically normal or near normal, degenerative changes exist in advanced OA patients. These changes can be detected with T2 and T1rho MRI techniques.

BACKGROUND: Alternative payment models aim to improve quality and decrease costs associated with total joint replacement. Postoperative readmissions within 90 days are of interest to clinicians and administrators as there is no additional reimbursement beyond the episode bundled payment target price. The aim of this study is to improve the understanding of the patterns of readmission which would better guide perioperative patient management affecting readmissions. We hypothesize that readmissions have different timing, location, and patient health profile patterns based on whether the readmission is related to a medical or surgical diagnosis. METHODS: A retrospective cohort of 80 readmissions out of 1412 total joint replacement patients reimbursed through a bundled payment plan was analyzed. Patients were grouped by readmission diagnosis (surgical or medical) and the main variables analyzed were time to readmission, location of readmission, and baseline Perioperative Orthopaedic Surgical Home and American Society of Anesthesiologists scores capturing pre-existing state of health. Nonparametric tests and multivariable regressions were used to test associations. RESULTS: Surgical readmissions occurred earlier than medical readmissions (mean 18 vs 33 days, P = .011), and were more likely to occur at the hospital where the surgery was performed (P = .035). Perioperative Orthopaedic Surgical Home and American Society of Anesthesiologists scores did not predict medical vs surgical readmissions (P = .466 and .879) after adjusting for confounding variables. CONCLUSION: Readmissions appear to follow different patterns depending on whether they are surgical or medical. Surgical readmissions occur earlier than medical readmissions, and more often at the hospital where the surgery was performed. The results of this study suggest that these 2 types of readmissions have different patterns with different implications toward perioperative care and follow-up after total joint replacement.

Femoral fractures between a total hip arthroplasty prosthesis and total knee arthroplasty prosthesis, also called interprosthetic fractures, are challenging clinical problems. The number of patients who have undergone ipsilateral primary or revision joint arthroplasty procedures in both the hip and the knee continues to rise, and the number of interprosthetic fractures is increasing, as well. The growing body of biomechanical and clinical literature on interprosthetic fractures reflects the increased frequency of and interest in these injuries. Similar to the management of periprosthetic fractures, the management of interprosthetic fractures depends on the location of the fracture, the stability of the implant, and the ability to achieve stable fracture fixation. These factors are the basis of recently described classification systems and treatment strategies. In patients with stable implants, fracture fixation alone is performed. When the implant is loose, both revision arthroplasty and fracture fixation may be required to provide stability of the limb.

PURPOSE: How changes in the surgical team's culture can potentially reduce operating room (OR) traffic. INTRODUCTION: Excessive OR traffic during surgical procedures can present a risk to the patient's safety and recovery. Data suggest that limiting the number of OR personnel during the intraoperative period can reduce excessive OR traffic. However, it is unclear whether the surgeon's verbal intervention can also successfully reduce intraoperative OR traffic. This study compares traffic rates in hip and knee arthroplasty cases against traffic rates during nonarthroplasty cases to examine the effects of verbal interventions implemented by the surgeon to reduce intraoperative traffic. METHOD: The study consisted of 16 orthopedic surgeons in a noninterventional group and 1 orthopedic surgeon in the interventional group. The surgeon in the interventional group implemented verbal protocols to OR staff to limit excessive intraoperative traffic. Operating room traffic was monitored for 3 consecutive months (January-March 2015) with the use of infrared automated door counters that tracked door openings when someone entered or left the OR. RESULTS: A total of 50 hip and knee arthroplasties cases and 157 nonarthroplasty cases were tracked during the study period. A total of 134 hours and 4482 movements were collected for the hip and knee arthroplasty cases. A total of 498 hours and 22 902 movements were collected for the nonarthroplasty cases. Comparing the 2 groups, the interventional group averaged 33 movements per hour while the noninterventional group averaged 46 movements per hour (P < .001). CONCLUSIONS: These results suggest that operative room traffic can be reduced through simple verbal protocols established by the surgical team.

Objective: To investigate indications for and outcomes of total hip and knee arthroplasty in patients with multiple sclerosis (MS). Background: MS patients may need joint replacement due to MS-related factors, such as falls or avascular necrosis, or for unrelated indications (eg primary/secondary osteoarthritis). Literature on outcomes of total joint replacement in MS patients is limited to case reports that highlight surgical complications or unusual presentations. There are no systematic reviews of indications for and short- and long-term outcomes of hip and knee arthroplasty in MS patients. Design/Methods: Retrospective chart review of NYU MS Center patients who underwent hip or knee arthroplasty after MS onset. Results: 13 MS patients followed at NYU MS Care Center underwent hip (N=8) or knee (N=5) replacement at NYU. Average age at surgery was 56+/-11 years (range 35-69 years) and MS duration was 16+/-9 years; 10/13 were female. 3 patients had prior joint trauma and 1 had avascular necrosis of the hip presumably from steroid use; the remainder suffered from osteoarthritis. Ambulatory status before surgery was: 4-walking unassisted, 7 - cane, 2 - bilateral assistance. Ambulatory status after surgery at last follow up was: 8 walking unassisted, 3 using a cane, and 2 using a walker. Perioperative complications included acute blood loss in 4, pneumonia in 2, DVT in 1, and urinary retention in 1. Reoperation was required in 1 patient for recurrent hip dislocation. Conclusions: Orthopaedic literature focuses on perioperative complications after total joint arthroplasty in MS patients, but our data on unselected patients show that the surgery appears to benefit most of them, though (mostly) non-neurologic complications were seen in approximately half of the cases. These data can help optimize selection and surgical management of MS patients who are considering knee or hip replacement. We intend to present additional data on our patients that will include patient-reported outcomes