Decreased patient comorbidities and post-operative complications in technology-assisted compared to conventional total knee arthroplasty.

PURPOSE: The use of computer-assisted and robotic surgery was developed to improve component position and outcomes of total knee arthroplasty (TKA). The goal of this study is to identify differences in patient demographics, comorbidities, and complications between technology-assisted and conventional TKA. METHODS: A Nationwide Inpatient Sample database was used to identify patients who underwent technology-assisted and conventional TKA from 2016 to 2018. Analysed variables include demographics, length of stay (LOS), payer-status, geographic region, comorbidities, complications, and mortality. Univariate and multivariate analyses were performed to identify differences between both groups. RESULTS: The analysis includes 2,208,434 TKA patients, of which 2,054,879 (93.05%) were conventional and 153,555 (6.95%) were technology assisted. Patients undergoing technology-assisted TKA were more likely to be older than 65 years, had higher median income quartile, and had surgery in urban teaching hospitals. Patients were less likely to undergo technology-assisted TKA if they were female gender, had Medicare payer status, were black race, were obese, were living in rural location, or had higher Charlson comorbidity score and baseline comorbidities. Technology-assisted TKA patients had shorter LOS, and fewer pulmonary and infection complications. CONCLUSION: Patients undergoing technology-assisted TKA are being carefully selected with less baseline comorbidities, improved health, and living in urban areas. Subsequently, those carefully selected patients are discharged home, have a shorted hospital LOS, and have fewer complications compared to conventional TKA. Rural patients, black race and female gender are less likely to undergo technology-assisted TKA, further emphasizing the healthcare disparity for that segment of the population. LEVEL OF EVIDENCE: Therapeutic level III.

Documented Penicillin Allergies Should Not Preclude Use of Preoperative Cefazolin in Hip and Knee Arthroplasty.

INTRODUCTION: Perioperative cefazolin administration for total joint arthroplasty is a first-line antibiotic recommended by the American Academy of Orthopaedic Surgeons (AAOS) guidelines for the prevention of periprosthetic joint infections (PJIs). We aim to analyze the clinical viability of giving patients with a documented penicillin allergy (PA) a perioperative full-strength cefazolin "test dose" under anesthesia. METHODS: This is a retrospective chart review of 2,451 total joint arthroplasties from a high-volume arthroplasty orthopaedic surgeon over a 5-year period from January 2013 through December 2017. This surgeon routinely gave patients with a documented PA a full-strength cefazolin test dose while under anesthesia instead of administrating a second-line antibiotic. The primary outcomes examined were allergic reaction and postoperative infection. RESULTS: Cefazolin was given to 87.1% of all patients (1,990) and 46.0% of patients with a PA (143). The total rate of allergic reactions among all patients was 0.5% (11). Only one patient with a documented PA who received cefazolin had an allergic reaction. The reaction was not severe and did not require any additional treatment. In patients who had no reported allergies and received cefazolin, 0.3% (6) had an allergic reaction. There was no statistically significant difference in the rate of allergic reaction when comparing patients with and without a PA (P = 0.95). Patients receiving cefazolin had an overall PJI rate of 2.9% (57) versus those patients receiving antibiotics other than cefazolin who sustained a 5.5% PJI rate (16), which was statistically significant (P = 0.02). CONCLUSION: This study found that utilization of a full-strength test dose of cefazolin in patients with a documented PA is a feasible, safe, and effective way of increasing the rate of cefazolin administration and thus mitigating the risk of PJIs.

Assessing the Weight-Bearing Surface in Dysplastic Acetabulae: The Sourcil Index.

BACKGROUND: Although a variety of standardized measurements have been described to evaluate acetabular dysplasia, no single measurement is without limitations. We describe the Sourcil Index (SI), a novel measure of the weight-bearing surface of the acetabulum on anteroposterior pelvis films. The SI is the angle formed by the medial and lateral margins of the sourcil and the center of rotation of the femoral head. METHODS: Anteroposterior pelvis radiographs of skeletally mature patients from 2015 were reviewed. Studies with fractures or implants were excluded. Films were read by 2 orthopedic surgeons and a radiologist 3 times each, 8 weeks apart. The SI, Sharp's Angle (SA), and lateral center edge angle (LCEA) were recorded. Pearson intraclass correlation coefficients with 95% confidence intervals were calculated. The SI was then compared to the SA and LCEA to preliminarily assess diagnostic accuracy. RESULTS: Five hundred thirty-five hips in 292 patients met inclusion. Intraobserver reliability is as follows: SI = 0.95 (0.93-0.98), LCEA = 0.89 (0.82 -0.96), and SA = 0.90 (0.85-0.96). Interobserver reliability is as follows: SI = 0.90 (0.84-0.94), SA = 0.78 (0.64-0.86), and LCEA = 0.73 (0.56-0.82). There were 51 dysplastic hips within this cohort. CONCLUSION: The SI is a reproducible measurement on plain radiographs. The SI is a two-dimensional representation of the size of the weight-bearing surface of the acetabulum and could provide an estimation of joint contact pressures. Used with existing measures, the SI may provide a more nuanced understanding of acetabular morphology.

Staged Total Hip Arthroplasty: A Novel Technique in Managing Native and Periprosthetic Acetabular Insufficiency.

BACKGROUND: There is no consensus on how to best address acetabular insufficiency. Several described techniques have a high rate of loosening and most rely on fixation to intact innominate bones. They also require extensive exposure and expensive implants. We present a novel technique for acetabular insufficiency management including discontinuity and a series with mean 6.5-year follow-up. MATERIAL AND METHODS: After exposure, a femoral neck osteotomy is made, or the femoral component is removed. Bone graft is reverse reamed into the defect, and a porous coated acetabular shell is implanted with screws for supplemental fixation. In 3-6 months, after defect healing, the femoral component is implanted. All staged total hip arthroplasties for pelvic discontinuity from 2010 to 2015 by a single provider with minimum 5-year follow-up were identified. Implant survivorship, Merle d'Aubinge, and visual analog scale scores as well as complications were recorded. RESULTS: Nine patients were identified with mean 80.8-month follow-up (62-129). Merle D'Aubinge scores improved from 5.6 (4-8) to 15.3 (14-18), and Visual analog scale scores improved from 7.2 (6-9) to 0.8 (0-2). All implants were retained, and all patients were ambulatory at the terminal follow-up. There were 2 greater trochanter fractures, one calcar fracture managed with cerclage, and one patient developed heterotopic ossification. CONCLUSION: Staged total hip arthroplasty can be used to address pelvic discontinuity with excellent short- to mid-term outcomes. This technique allows for a more limited exposure and the use of primary hip implants. Fixation is by ingrowth and does not rely on intact pelvic architecture.

Morphology of the Greater Trochanter: An Assessment of Anatomic Variation and Canal Overhang.

BACKGROUND: Varus malposition is a risk of early failure in total hip arthroplasty. The degree to which the tip of the greater trochanter (GT) overhangs the canal can increase this risk. Although we know proximal femoral anatomy is variable, no study has addressed variations in medial overhang of the GT on plain radiographs. METHODS: All low anteroposterior pelvis radiographs more than 1 year were reviewed 3 times by 2 orthopaedic surgeons and one radiologist. The canal width (CW) was measured 10 cm below the lesser trochanter. Canal overhang (CO) was defined by the distance between the lateral medullary canal and a parallel line beginning at the most medial aspect of the GT. The overhang index (OI) is defined as the percentage of the canal overhung by the GT. RESULTS: The mean CW was 13.5 mm, mean CO 16.4 mm, and mean OI 1.22. Hips were then classified as the following: (A) OI < 0.5 (n = 8), (B) OI 0.5-1.0 (n = 78), (C) OI 1.0-1.5 (n = 191), and (D) OI > 1.5 (n = 68). Intraobserver reliability was excellent for all measures: 0.89 (confidence interval: 0.87-0.91) for CW, 0.96 (0.95-0.97) for CO, and 0.97 (0.97-0.98) for OI. Interobserver reliability was good for CW 0.75 (0.70-0.79) and excellent for CO 0.90 (0.88-0.92) and OI 0.95 (0.94-0.96). CONCLUSIONS: Variations in the morphology of the proximal femur can predispose to varus component malposition. The degree to which the GT overhangs the canal can be quantified and classified based on plain films. This can aid in preoperative planning and help guide intraoperative proximal femoral preparation.

Surgical simulators and hip fractures: a role in residency training?

BACKGROUND: Orthopedic surgery residency training requires intellectual and motor skill development. In this study, we utilized a computer-based haptic simulator to examine a potential model for evaluation of resident proficiency and efficiency in the placement of a center guide wire during fixation of an intertrochanteric proximal femur fracture. We hypothesize the junior residents will utilize more fluoroscopy and require more time to complete the task. METHODS: Postgraduate year (PGY) 1-5 residents completed the same task of placing a single central guide pin into a femoral head for a dynamic hip screw construct utilizing a haptic surgical simulator. Residents were divided into 2 groups (PGY 1-2 and PGY 3-5) and then evaluated based on final tip-apex distance (TAD), fluoroscopy time, time to complete the task, total number of distinct attempts at pin placement for each femur construct, as well as final 3-dimensional location of the pin from the isometric center of the femoral head. RESULTS: No statistically significant differences were noted between the 2 groups in total time or for tip-apex distance, anterior/posterior medial/lateral position, anterior/posterior superior/inferior, and lateral x-ray medial/lateral positioning measurements. Significant differences between Groups I and II were observed in anterior/posterior final position on the lateral view (p = 0.01), unique attempts (0.77 and 1.5, p = 0.03), and total fluoroscopic time (18.4 seconds and 12.9 seconds, p = 0.05). CONCLUSIONS: In this study, we displayed that based on our simulator model there was no statistical difference between Group I and II in time to completion, final placement on anterior/posterior (A/P) view, and tip-apex distance. There was a statistically significant difference in the anterior/posterior placement of the wire in lateral view between the 2 groups, fluoroscopy time, and number of attempts per trial. Our findings suggest a computer-based surgical simulator can identify measurable differences in surgical proficiency between junior and senior orthopedic surgery residents and may play an expanding role in resident education.

Radiographic evaluation of midterm failure rates following metal-on-metal hip resurfacing.

This prospective study examined patient characteristics and radiographic findings for 89 subjects undergoing total hip resurfacing. Thirteen (14.6%) of 89 hips have required revision. Female sex, smaller implant size, and diagnosis of osteonecrosis were associated with lower device survival. No significant differences in acetabular cup angle and stem angle were observed between revised and nonrevised hips. Revision rates for the first 25 hips were 24% and 8% for the last 64 hips. Females accounted for 56% of subjects 1 to 25 and 23% of subjects 26 to 89. Despite representing only 33% of included subjects, females accounted for 62% of revision procedures. The lower device survival proportion in subjects 1 to 25 could not be attributed to acetabular or femoral component malpositioning and can likely be explained by a significantly higher proportion of females enrolled early in the study.

Hospital outcome after emergent vs elective revision total hip arthroplasty.

This is a retrospective review of inpatient outcomes, based upon emergent or elective admission for revision total hip arthroplasty (THA) procedures performed between 2000 and 2006. Three hundred forty-two revision THA procedures (291 elective, 51 emergent) were identified. Emergent revisions were more likely to be older (69.9 vs 62.7; P = .003), women (72% vs 54%), require longer hospitalization (8.3 vs 3.8 days), and require a skilled care facility at discharge. No significant difference was observed in mortality. We identified 2 basic outcome measures suggesting that patients undergoing emergent revision will have a more complex hospitalization and require more assistance at discharge. Clarifying emergent vs elective THA at admission may assist in better planning and assessment of patient needs regarding rehabilitation, hospital management, and discharge planning.

Effect of hand packing versus cement gun pressurization on cement mantle in total knee arthroplasty.

BACKGROUND: Gun pressurization in total knee arthroplasty (TKA) may result in better cement penetration than hand packing, leading to fewer tibial plate failures. We compared cement intrusion characteristics between vacuum mixing and gun pressurization versus hand mixing and packing in the proximal tibia among patients undergoing TKA. METHODS: We analyzed 6-week radiographs from 77 consecutive patients for cement area and zone-specific intrusion using computer-assisted image analysis. RESULTS: Penetration into tibial anteroposterior zones 1-6 was not significantly different between the techniques. Intrusion depths in anteroposterior zone 7 and lateral zone 2 were significantly increased with gun pressurization, but this increase was associated with significantly longer operating room and tourniquet times. CONCLUSION: We identified no obvious advantage of vacuum mixing with gun pressurization, suggesting that continued use of the hand-packing technique may be warranted. Additional long-term failure studies must be completed to compare these techniques.

Effect of bone cement viscosity and set time on mantle area in total knee arthroplasty.

To assess the impact of bone cement viscosity on total knee arthroplasty, we compared 1 high-viscosity and 2 medium-viscosity cements with respect to mantle area and zone-specific intrusion depths into the tibial plateau. We analyzed postoperative radiographs to determine penetration area and depth in 72 consecutive patients (79 knees) in whom DePuy II (n = 11), Endurance (n = 34), or Simplex-P (n = 34) cement was used. Penetration into the tibial plateau (anteroposterior zones 1-4) was significantly reduced with use of the high-viscosity DePuy II cement but did not differ significantly between the 2 medium-viscosity cements, Endurance and Simplex-P. Surgical and tourniquet times were significantly decreased with the quicker setting DePuy II cement. Given these findings, additional studies are warranted to assess the long-term impact of the lower intrusion depths found with DePuy II cement. Such differences in cement penetration could jeopardize long-term fixation and lead to higher long-term device failure rates.

Acetabular cup malalignment after total hip resurfacing arthroplasty: a case for elective revision?

This article describes the clinical course of a patient with a resurfacing implant in a poor cup position in combination with elevated serum metal ions prior to implant failure. Following resurfacing, the patient had substantial improvement from baseline in pain and functional status. Postoperative radiographs indicated the acetabular cup in an abducted and excessively anteverted position. The acetabular component ultimately failed after 4.5 years and a traditional total hip arthroplasty revision was performed. Serum cobalt (Co) and chromium (Cr) concentrations had been collected postoperatively of the index procedure at 6 months, 1 year, 2 years, 3 years, and pre- and postoperatively at the time of implant revision. Serum cobalt and chromium ion levels were progressively elevated to approximately 400 times more than the expected range at all time points prior to revision. Elective revision had been considered due to acetabular malalignment and elevated metal ion levels, but not performed since the patient was doing well clinically. A recent study has shown a correlation between increased cup inclination and increased serum cobalt or chromium levels and this patient's levels were >40 times greater than that typically observed with this device. Early revision should be strongly considered if component malpositioning is noted, and abnormally elevated ion concentrations should signal the need for revision regardless of the patient's clinical status. The relationship of a malpositioned cup and uncharacteristically elevated metal ion levels is related to the metal-on-metal bearing coupling and likely applies to conventional metal-on-metal total hip prostheses as well.

Are honors received during surgery clerkships useful in the selection of incoming orthopaedic residents?

The purpose of this study was to review institutional statistics provided in dean's letters and determine the percentage of honors awarded by institution and clerkship specialty.Institutional and clerkship aggregate data were compiled from a review of dean's letters from 80 United States medical schools. The percentage of honors awarded during 3rd year clerkships during 2005 were collected for analysis. Across clerkship specialties, there were no statistically significant differences between the mean percentage of honors given by the medical schools examined with Internal Medicine (27.6%) the low and Psychiatry (33.5%) the high. However, inter-institutional variability observed within each clerkship was high, with surgery clerkship percentage of honors ranging from 2% to 75% of the students. This suggests some schools may be more lenient and other more stringent in awarding honors to their students. This inter-institutional variability makes it difficult to compare honors received by students from different medical schools and weakens the receipt of honors as a primary tool for evaluating potential incoming residents.

Impact of the 80-hour workweek on surgical exposure and national in-training examination scores in an orthopedic residency program.

OBJECTIVES: This study examines the impact of the 80-hour workweek on the number of surgical cases performed by PGY-2 through PGY-5 orthopedic residents. We also evaluated orthopedic in-training examination (OITE) scores during the same time period. METHODS: Data were collected from the Accreditation Council for Graduate Medical Education (ACGME) national database for 3 academic years before and 5 years after July 1, 2003. CPT surgical procedure codes logged by all residents 3 years before and 5 years after implementation of the 80-hour workweek were compared. The average raw OITE scores for each class obtained during the same time period were also evaluated. Data were reported as the mean +/- standard deviation (SD), and group means were compared using independent t-tests. RESULTS: No statistical difference was noted in the number of surgical procedure codes logged before or after the institution of the 80-hour week during any single year of training. However, an increase in the number of CPT codes logged in the PGY-3 years after 2003 did approach significance (457.7 vs 551.9, p = 0.057). Overall, the average number of cases performed per resident increased each year after implementation of the work-hour restriction (464.4 vs 515.5 cases). No statistically significant difference was noted in the raw OITE scores before or after work-hour restrictions for our residents or nationally. CONCLUSIONS: We found no statistical difference for each residency class in the average number of cases performed or OITE scores, although the total number of cases performed has increased after implementation of the work-hour restrictions. We also found no statistical difference in the national OITE scores. Our data suggest that the impact of the 80-hour workweek has not had a detrimental effect on these 2 resident training measurements.

Multi-modal, pre-emptive analgesia decreases the length of hospital stay following total joint arthroplasty.

Traditional treatment of pain following total joint arthroplasty involves postoperative oral narcotic medications and intravenous patient-controlled analgesia, both of which can result in significant postoperative morbidity. Multi-modal analgesia involving >or=2 classes of drugs acting on different receptor types may be as effective as single-narcotic/patient-controlled analgesia with fewer analgesic-related side effects. In addition, administering analgesia prior to surgery (pre-emptive) may reduce postoperative pain intensity. The current study was designed to compare the impact of multi-modal pre-emptive analgesia versus patient-controlled analgesia on postoperative nausea, rehabilitation participation, and length of stay following total joint arthroplasty. A retrospective chart review and comparison was performed for patients undergoing total joint arthroplasty who received either postoperatively patient-controlled analgesia or pre-emptive analgesia (scheduled postoperative oxycodone and a COX-2 inhibitor). Length of hospital stay for the pre-emptive group averaged 2.74 vs 3.28 days for patient-controlled analgesia patients. The patient-controlled analgesia group consumed significantly more intravenous morphine (17.7 mg vs 7.2) and experienced a three-fold increase in nausea. In addition, the patient-controlled analgesia group was twice as likely to miss therapy and nearly 2 times more likely to be discharged to an extended care facility. The use of pre-emptive oxycodone and a selective COX-2 inhibitor decreased postoperative narcotic requirements and increased participation in rehabilitation. In addition, patients receiving pre-emptive analgesics had a decreased hospital length of stay and reduced likelihood of discharge to a skilled nursing facility. These data support the continued study and use of pre-emptive multi-modal analgesia paradigms in this population.

Serum cobalt and chromium elevations following hip resurfacing with the Cormet 2000 device.

This study was designed to monitor serum cobalt (Co) and chromium (Cr) levels at multiple time points following hip resurfacing with the Cormet 2000 device. Serum samples were obtained preoperatively, at 6 months, 1, 2, and 3 years after surgery. Co/Cr levels (micro g/L) were determined by high-resolution inductively coupled plasma mass spectrometry. Thirty-five subjects were followed. Median preoperative Co/Cr levels were 0.21 and 0.22, respectively. Serum levels following device implantation were increased at all follow-up time points when compared to preoperative controls. Peak levels were observed at 1 year (Co, 3.34; Cr, 4.67) and levels at 3 years were trending down (Co, 2.08; Cr, 3.55), but this decrease was not statistically significant. This study is the first to report significant elevations in serum Co/Cr levels at multiple time points up to 3 years following hip resurfacing with the Cormet 2000 device. Future studies are needed to determine what serum Co/Cr levels are of clinical concern, particularly in outlier cases.

Clonality studies in sacral chordoma.

Chordomas are rare, slow-growing, primary malignant skeletal neoplasms. Chromosome analysis, telomere reduction and telomere activity, DNA microsatellite, and loss of heterozygosity studies have been performed on chordomas; however, the clonality status (monoclonal versus polyclonal proliferation) is unknown. The primary purpose of this study was to determine whether sacral chordoma is monoclonal or polyclonal in origin with the use of a polymorphic X-linked gene (AR; alias HUMARA) and X-chromosome inactivation studies. DNA was harvested from tumor and corresponding normal tissue from eight women (37-71 years) with chordoma. Clonality was determined using an X chromosome inactivation protocol and a polymorphic human androgen receptor gene (AR) located on the X chromosome. The procedure required a methylation-specific polymerase chain reaction (PCR) and determination of the ratio of active to inactive X chromosomes. Results were informative for seven of the eight women, with two separate X-linked alleles seen for the AR gene in the normal tissue. Expression of AR gene alleles from each of the two X chromosomes was present in the chordoma tumor, indicating a polyclonal proliferation in all seven women. Most solid tumors and skeletal neoplasms are polyclonal in nature. Our study indicates that chordoma is polyclonal in its pattern of proliferation.

The use of proximal fixed modular stems in revision of total hip arthroplasty.

Proximally fixed femoral stems in revision of total hip arthroplasties (THAs) have had inconsistent results. Our aim was to determine the safety and efficacy of a new proximally fixed modular stem in THA revision. Fifty-three patients underwent THA revision with the Exactech AccuMatch M-Series (Gainesville, Fla) modular stem and were followed up prospectively for an average of 2.5 years with preoperative and postoperative Harris Hip Score and SF-12 scores. A small number of complications were reported. One stem was revised within 4 weeks due to subsidence. No later mechanical failure cases were reported. Postoperative Harris Hip Score and SF-12 improved significantly. The use of this modular stem system appears to be safe and efficacious regarding fixation and function in the short term.

Trochanteric fixation in total hip arthroplasty using the S-ROM bolt and washer.

We evaluated the S-ROM bolt and washer (DePuy, Inc, Warsaw, IN) for fixation of the greater trochanter after trochanteric osteotomy in 29 hips in 28 consecutive patients. Of 29 cases, 9 (31%) resulted in trochanteric nonunion, with bony union being achieved in only 38% of cases. There was dislocation and subluxation in 7 of 29 (24%) cases with 6 of the 7 dislocations associated with trochanteric nonunion. Revision was necessary in 4 of 8 hips to obtain fixation of the trochanter. The rate of complications in this series suggests that the S-ROM bolt and washer is associated with a high rate of nonunion, particularly in the multiply-revised hip. Avoidance of trochanteric osteotomy whenever possible would be desirable. When an osteotomy is necessary, alternative forms of fixation should be considered.