Faculty Bibliography

BACKGROUND: A large component of the cost of revision total hip arthroplasty (THA) is the cost of the implants. We examined the pricing of revision THA implants to determine the possible savings of different pricing models. METHODS: From our institutional database, all revision THAs done from 9/1/2013 to 8/31/2014 were identified. The cost of the implants was analyzed as a percentage of the total cost of the hospitalization and compared to direct to hospital and fixed implant pricing models. RESULTS: Of 153 revision THAs analyzed, the cost of implants amounted to 36% of the total hospital cost. The direct to hospital cost and fixed implant pricing models would reduce the cost of an all-component revision to $4395 (saving $8962 per case) and $5000 (saving $8357 per case). CONCLUSION: Both fixed implant pricing and the direct to hospital pricing models would result in a decrease in revision implant costs.

BACKGROUND: Short-term and intermediate-term wear rates for highly cross-linked polyethylene (HCLPE) liners in total hip arthroplasty (THA) are significantly lower than published rates for traditional polyethylene liners. The aim of this study was to report the longest-to-date follow-up of a specific HCLPE liner. METHODS: A series of 35 THAs using a specific HCLPE liner were reviewed. Anteroposterior radiographs were reviewed for femoral head penetration, the presence of femoral and/or acetabular osteolysis, long-term survival, total wear, and wear rates in all patients. RESULTS: The average patient age at time of surgery was 70 years with an average follow-up of 10 years (118 months; range, 7.2-13.4 years). The mean wear rate in our cohort was 0.07 mm/y. Total wear was 0.71 mm over the study period. No hips showed evidence of osteolysis in any zones. Survivorship at latest follow-up was 100% with all-cause revision as an end point. CONCLUSION: The wear rate of HCLPE liners continues to be lower than published wear rates for traditional polyethylene and continues to reaffirm the acceptably low wear rates using HCLPE acetabular liner in primary THA.

BACKGROUND: Accurate measurement of acetabular cup position (CP), changes in leg length (LL), and offset (OS) are paramount in ensuring proper sizing and implantation of components during total hip arthroplasty (THA). LL/OS inaccuracies can cause low back pain, neurological deficits, and patient dissatisfaction, while inaccurate positioning of the acetabular cup can lead to instability, dislocation, and, ultimately, revision surgery. The objective of this study was to evaluate the accuracy of a mini-navigation tool in measuring CP and LL/OS differential during THA. MATERIALS AND METHODS: Three board-certified orthopedic surgeons each performed four THA procedures via the posterior approach on six cadavers (12 hips) utilizing a novel mini-navigation tool. Imaging included pre- and post-operative radiographs and post-operative CT scans. Image analysis was performed by two radiologists not involved in the surgical procedures. System accuracy regarding measurement of cup position (anteversion and inclination) was determined by comparing the CT measurement of cup orientation with data gathered intraoperatively by probing the face of the implanted cup with the navigation tool and recording the coordinates. RESULTS: The mean absolute difference between CT and device measurements of cup position was 0.74 masculine (SD: 0.47, range: 0.19-1.48) for anteversion and 0.97 masculine (SD: 0.67, range: 0.27-2.57) for inclination. The mean difference between device and radiograph measurements of LL changes was 0.27 mm (SD: 3.61, range: -5.20-7.78) (absolute mean: 2.71+/-2.25 mm), while the mean difference in OS was 1.75 mm (SD: 3.00, range: -2.47-6.65) (absolute mean: 2.37+/-2.44 mm). CONCLUSIONS: This novel mini-navigation tool measured CP, LL, and OS accurately when compared with implant position measured on imaging.

PURPOSE: The objective of this study was to quantify the amount of ensuing internal rotation of the tibial component when positioned along the medial border of the tibial tubercle, thus establishing a reproducible intraoperative reference for tibial component rotational alignment during total knee arthroplasty (TKA). METHODS: The angle formed from the tibial geometric centre to the intersection of both lines from the middle of the tibial tuberosity and its medial border was measured in 50 patients. The geometric centre was determined on an axial CT slice at 10 mm below the lateral tibial plateau and transposed to a slice at the level of the most prominent part of the tibial tuberosity. Similar measurements were taken in 25 patients after TKA, in order to simulate the intraoperative appearance of the tibia after making its proximal resection. RESULTS: This angle was found to be similar (n.s.) in normal and post-TKA tibiae [median 20.4 degrees (range 15 degrees -24 degrees ) vs. 20.7 degrees (range 16 degrees -25 degrees ), respectively]. In 89.3 % of the patients, the angle ranged from 17 degrees to 24 degrees . No statistical difference (p n.s.) was found between women and men in both normal [median -20.7 degrees (range 16 degrees -25 degrees ) vs. 19.9 degrees (range 15 degrees -24 degrees )] and post-TKA tibiae [median 21.4 degrees (range 19 degrees -24 degrees ) vs. 20 degrees (range 16 degrees -25 degrees )]. CONCLUSION: This study found that in 90 % of the patients, the medial border of the tibial tuberosity is internally rotated 17 degrees -24 degrees in relation to the line connecting the middle of the tuberosity to the tibial geometric centre. Since this anatomical landmark may be more easily identifiable intraoperatively than the commonly used "medial 1/3", it can provide a better quantitative reference point and help surgeons achieve a more accurate tibial implant rotational position. LEVEL OF EVIDENCE: Cohort and case control studies, Level III.

BACKGROUND: To our knowledge, no study has assessed the ability of rigid patient positioning devices to afford arthroplasty surgeons with ideal acetabular orientation throughout surgery. The purpose of this study is to use robotic arm-assisted computer navigation to assess the reliability of pelvic position in total hip arthroplasty performed on patients positioned with rigid positioning devices. METHODS: A prospective cohort of 100 hips (94 patients) underwent robotic-guided total hip arthroplasty in the lateral decubitus position from the posterior approach, 77 stabilized by universal lateral positioner, and 23 by peg board. Before reaming, computed tomography-templated computer software generated true values of pelvic anteversion and inclination based on the position of the robot arm registered to the patient's preoperative pelvic computed tomography. RESULTS: Mean alteration in anteversion and inclination values was 1.7 degrees (absolute value, 5.3 degrees ; range, -20 degrees to 20 degrees ) and 1.6 degrees (absolute value, 2.6 degrees ; range, -8 degrees to 10 degrees ), respectively. And 22% of anteversion values were altered by >10 degrees and 41% by >5 degrees . There was no difference between hip positioners used (P = .36). Anteversion variability was correlated with body mass index (P = .02). CONCLUSION: Despite the use of rigid patient positioning devices-a lateral hip positioner or peg board-this study reveals clinically important malposition of the pelvis in many cases, especially with regard to anteversion. These results show a clear need to pay particular attention to anatomic landmarks or computer-assisted techniques to assure accurate acetabular cup positioning. Patient positioning should not be solely trusted.

OBJECTIVE: Orthopedic residents commonly perform closed manipulative reductions as a part of their training. Traditionally, this skill is taught early in training but difficult to simulate. Proficiency is achieved through repetition and experience; faculty observation and instruction is unfortunately often limited. Direct resident teaching has been shown to increase competency, comfort, and long-term skill retention. We hypothesize that video review of closed fracture reductions will provide an inexpensive and valuable tool for resident education and improve skill performance. DESIGN: Closed reductions performed by orthopaedic residents were recorded using a secured mobile tablet device in the emergency department (ED). Video review sessions were performed with both peer and faculty feedback/analysis of reduction technique. Anonymous resident and faculty surveys were completed following each session to evaluate the usage and perceived benefit of the program. SETTING: University-based Level I Trauma Center. PARTICIPANTS: Orthopedic surgery residents and faculty. RESULTS: All junior orthopedic residents (postgraduate year [PGY] 1-3) reported that direct video observation by faculty was beneficial. Furthermore, 97% of junior resident and 100% of faculty responses reported that they would use this educational technology in the future. Residents and faculty both strongly agreed that video review was more useful than other methods, improved resident preparation for ED fracture care, and felt this technique would improve patient care and outcomes. Compared with senior residents (PGY 4-5), PGY-1s believed that this technique helped them prepare for ED fracture care (p = 0.02). CONCLUSIONS: Video review provides a useful, innovative, and inexpensive method to improve resident competency in closed fracture reduction-a critical skill in orthopedic patient care. These procedures are uncommonly available for direct faculty observation. We have demonstrated that both residents and faculty were satisfied with the ability to review procedures, identify weaknesses, and obtain or provide direct feedback on this skill. Additionally, fracture reduction video review may help residents meet and achieve clinical milestones, an area of future investigation.

BACKGROUND: Changes in spinal alignment and pelvic tilt alter acetabular orientation in predictable ways, which may have implications on stability of total hip arthroplasty (THA). Patients with sagittal spinal deformity represent a subset of patients who may be at particularly high risk of THA instability because of postural compensation for abnormal spinal alignment. METHODS: Using standing stereoradiography, we evaluated the spinopelvic parameters, acetabular cup anteversion, and inclination of 139 THAs in 107 patients with sagittal spinal deformity. Standing images were compared with supine pelvic radiographs to evaluate dynamic changes in acetabular cup position. Dislocation and revision rates were procured through retrospective chart review. The spinal parameters and acetabular cup positions among dislocators were compared with those who did not dislocate. RESULTS: The rate of THA dislocation in this cohort was 8.0%, with a revision rate of 5.8% for instability. Patients who sustained dislocations had significantly higher spinopelvic tilt, T1-pelvic angle, and mismatch of lumbar lordosis and pelvic incidence. Among all patients, 78% had safe anteversion while supine, which decreased significantly to 58% when standing due to increases in spinopelvic tilt. Among dislocating THA, 80% had safe anteversion, 80% had safe inclination, and 60% had both parameters within the safe zone. CONCLUSION: In this cohort, patients with THA and concomitant spinal deformity have a particularly high rate of THA instability despite having an acetabular cup position traditionally thought of as within acceptable alignment. This dislocation risk may be driven by the degree of spinal deformity and by spinopelvic compensation. Surgeons should anticipate potential instability after hip arthroplasty and adjust their surgical plan accordingly.

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.