Faculty Bibliography

INTRODUCTION/BACKGROUND:Loosening and migration are common modes of aseptic failure following complex revision total knee arthroplasty (rTKA). Metaphyseal cones allow surgeons to negotiate the loss of femoral and tibial bone stock while obtaining stable bony fixation. This study examines the mid-term functional and radiographic outcomes in patients undergoing rTKA utilizing a novel metaphyseal cone system with stems of variable length and fixation methods. METHODS:This two-center retrospective study examined all patients who underwent rTKA with a novel porous, titanium tibial or femoral cone in combination with a stem of variable length and fixation who had a minimum follow-up of 2-years. Outcome analysis was separated into tibial and femoral cones as well as the stem fixation method (hybrid vs. fully cemented). RESULTS:Overall, 123 patients who received 156 cone implants were included (74 [60.2%] tibial only, 16 [13.0%] femoral only, and 33 [26.8%] simultaneous tibial and femoral) with a mean follow-up of 2.76 ± 0.66 years. At 2-years of follow-up the total cohort demonstrated 94.3% freedom from all-cause re-revisions, 97.6% freedom from aseptic re-revisions, and 99.4% of radiographic cone osteointegration. All-cause revision rates did not differ between stem fixation techniques in both the tibial and femoral cone groups. CONCLUSION/CONCLUSIONS:The use of a novel porous titanium femoral and tibial metaphyseal cones combined with stems in patients with moderate to severe bone defects undergoing complex revision total knee arthroplasty confers excellent results independent of stem fixation technique. LEVEL OF EVIDENCE/METHODS:IV, case series.

Cam-post dislocations are a unique complication of total knee arthroplasty (TKA) designs that utilize a cam-post mechanism, representing an extreme form of deep flexion instability. They are rare complications and are poorly defined in the existing literature. The purpose of this case study is to present a series of six cam-post dislocation cases to improve understanding of this complication and its mechanism, presentation, and available treatment options. All patients experienced cam-post dislocations after a deep flexion moment that were identified clinically and confirmed radiographically. Affected implants included both primary and revision components and all utilized a cam-post mecha- nism. Three patients underwent revision surgery whereas the remaining three were treated with closed reduction only. Cam-post dislocations are rare complications of posterior- stabilized TKA that should be understood and recognized by adult reconstruction surgeons. Closed reduction may be achieved with hyperflexion and anterior drawer or with hyperextension, but these patients may ultimately require a revision procedure.

INTRODUCTION/BACKGROUND:Computer-assisted navigation systems (CAS) are increasingly being integrated into total knee arthroplasty (TKA) procedures, but perceptions of associated learning curve and increased operative time continue to curtail uptake. Newer-generation navigational systems aim to streamline integration into surgical workflow to mitigate increases in operative time. Here, we assess the impact of a novel imageless CAS on operative time for TKA. METHODS:A retrospective analysis of prospectively collected data of a cohort of patients undergoing primary unilateral TKA with one of three surgeons between October 2019 and March 2020 was conducted. Consecutive cases using a novel imageless CAS were included in analysis. For each surgeon, average operative time was recorded and compared in sequential five-case cohorts to average operative time for the same procedure performed conventionally using a two-tailed t test. RESULTS:Average conventional operative times were 95.9 ± 15.0, 86.6 ± 13.7, and 116.9 ± 25.1 min for the three surgeons. Initial CAS-assisted operative times increased to 107.0 ± 9.8 (p = 0.07) and 102.4 ± 13.2 (p = 0.06) min for Surgeons 1 and 2 and decreased to 113.2 ± 9.8 min (p = 0.52) for Surgeon 3. Most recent CAS-assisted operative times were 94.8 ± 13.9 (p = 0.88), 88.7 ± 15.3 (p = 0.84), and 104.8 ± 13.2 (p = 0.12) min as compared to pre-CAS. Absolute differences for the most recent navigated procedures ranged from 12.1 min faster to 2.0 min slower. CONCLUSION/CONCLUSIONS:The learning curve for TKA navigation may be as few as 10 cases, and any associated increases in operative time may be transient and non-significant. Moreover, navigation may ultimately speed operative time, perhaps as the result of enhanced intraoperative assessment of alignment.

PURPOSE/OBJECTIVE:Navigated total knee arthroplasty (TKA) improves implant alignment by providing feedback on resection parameters based on femoral and tibial cutting guide positions. However, saw blade thickness, deflection, and cutting guide motion may lead to final bone cuts differing from planned resections, potentially contributing to suboptimal component alignment. We used an imageless navigation device to intraoperatively quantify the magnitude of error between planned and actual resections, hypothesizing final bone cuts will differ from planned alignment. MATERIALS AND METHODS/METHODS:A retrospective study including 60 consecutive patients undergoing primary TKA using a novel imageless navigation device was conducted. Device measurements of resection parameters were obtained via attachment of optical trackers to femoral and tibial cutting guides prior to resection. Following resection, optical trackers were placed directly on the bone cut surface and measurements were recorded. Cutting guide and bone resection measurements of both femoral and tibial varus/valgus, femoral flexion, tibial slope angles, and both femoral and tibial medial and lateral resection depths were compared using a Student's t-test. RESULTS:Femoral cutting guide position differed from the actual cut by an average 0.6 ± 0.5° (p = 0.85) in the varus/valgus angle and 1.0 ± 1.0° (p = 0.003) in the flexion/extension angle. The difference between planned and actual cut measurements for medial and lateral femoral resection depth was 1.1 ± 1.1 mm (p = 0.32) and 1.2 ± 1.0 mm (p = 0.067), respectively. Planned cut measurements based on tibial guide position differed from the actual cut by an average of 0.9 ± 0.8° (p = 0.63) in the varus/valgus angle and 1.1 ± 1.0° (p = 0.95) in slope angle. Measurement of medial and lateral tibial resection depth differed by an average of 0.1 ± 1.8 mm (p = 0.78) and 0.2 ± 2.1 mm (p = 0.85), respectively. CONCLUSIONS:Significant discrepancies between planned and actual femoral bone resection were demonstrated for flexion/extension angle, likely the result of cutting error. Our data highlights the importance of cut verification postresection to confirm planned resections are achieved, and suggests imageless navigation may be a source of feedback that would allow surgeons to intraoperatively adjust resections to achieve optimal implant alignment.

CASE REPORT:A 67-year-old man presented with signs of acute periprosthetic infection after total hip arthroplasty (THA). Surgical debridement, antibiotics, and a head and liner exchange were performed. After showing no improvement, a single-stage revision was conducted. Postoperatively, he developed back pain and lower extremity weakness. Electrodiagnostic studies showed a Guillain-Barré syndrome (GBS) variant. Intravenous immunoglobulin was administered to halt disease progression. After 1 year, he still demonstrated neuromuscular deficits and required a cane for ambulation. CONCLUSION:This case highlights GBS after THA. A high degree of clinical suspicion is essential to prevent misinterpretation as a postsurgical complication. LEVEL OF EVIDENCE:V, case report.

Same-day discharge (SDD) surgery in total hip arthroplasty (THA) has been shown to have similar outcomes to non-SDD THA in select patient populations. Hip resurfacing arthroplasty (HRA) is an alternative to THA for young, active patients, making them ideal candidates for SDD. This study compared the safety and efficacy of non-SDD HRA and SDD HRA for specific postoperative outcomes. An electronic data warehouse query was performed for procedures labeled "hip resurfacing." Data collected included demographics, surgical factors, and quality metrics. Statistical analyses were evaluated using a graphing and statistics software program. Categorical variables were analyzed with chi-square tests and continuous variables with Student's t tests, with P<.05 deemed significant. Sixty-three of 274 total HRAs were enrolled in this SDD HRA protocol. No significant difference was observed between SDD HRA and non-SDD HRA baseline characteristics. On postoperative day 0, 98.41% of SDD HRA recipients were discharged successfully. The SDD HRA recipients had shorter stays, with 1.59% requiring a hospital stay of 2 days or more compared with 56.87% of non-SDD HRA recipients (P<.0001). The non-SDD HRA recipients were found to have shorter surgical times than SDD HRA recipients (104.74 vs 125.51 minutes, P=.01). Rates of infection, periprosthetic fractures, emergency department visits, and hospital readmissions were equivalent (P=.99). Same-day discharge HRA is a safe and effective procedure with similar outcomes to non-SDD HRA regarding infections, fractures, emergency department visits, and readmissions. The major benefit of SDD is a shorter hospital stay that may lead to decreased cost while preserving and enhancing quality of care and patient satisfaction. [Orthopedics. 2020;43(6):e595-e600.].

PURPOSE/OBJECTIVE:There has been an increase in the use of unlinked constrained condylar knee (CCK) prostheses in primary total knee arthroplasty (TKA) for cases with significant deformities that cannot be adequately balanced in flexion and extension. However, the literature on its outcomes is limited. The goal of this study is to evaluate whether there are any clinic or radiographic outcome differences for a primary, non-stemmed, unlinked constrained TKA as compared to a control group of posterior-stabilized (PS) TKA using the same implant design. METHODS:Clinical and radiographic outcome measures for 404 cemented, non-stemmed, primary TKAs performed by two surgeons at the same institution were retrospectively reviewed. All patients underwent primary, non-stemmed components; 241 used CCK inserts and 163 used PS inserts. Preoperative deformity, knee society scores (KSS), range-of-motion (ROM), radiographic data and revision rates were compared between the CCK and PS groups. RESULTS:Both groups had comparable demographics and preoperative ROM and KSS. At similar mean follow-up times (6.1 ± 1.0 years for the CCK group and 6.3 ± 1.2 years for the PS group), no significant difference was found in ROM, KSS or radiographic outcomes. Revision rates were higher for the CCK group (2%) as compared to the HF-PS (0.6%) group (n.s). CONCLUSIONS:The particular design of cemented, primary, non-stemmed, unlinked CCK-TKA examined in this study provided similar clinical and radiographic outcomes to that of PS-TKA at midterm follow-up. LEVEL OF EVIDENCE/METHODS:III.

BACKGROUND:Short-stem (SS) hip prostheses for total hip arthroplasty (THA) have gained popularity as surgeons strive to reproduce physiological stress distributions at the proximal femur. Additionally, as THA indications continue to target younger populations, preservation of femoral bone stock for potential revision surgeries is particularly appealing. However, little is known regarding the short-term complications of each variety of short stem during the learning curve period. The purpose of this study is to evaluate the short-term complications among the THA recipients with the use of a novel SS hip prosthesis. METHODS:A retrospective chart review was performed of all patients undergoing primary THA utilizing an Echo Bi-Metric Microplasty hip stem. Patient demographics, surgical factors, complications and quality outcomes were collected utilizing our institution's data warehouse and verified by chart review. RESULTS:In total, 182 SSs were implanted in 168 patients undergoing primary THA. Of these, 5 (2.9%) patients sustained a periprosthetic fracture. Two fractures occurred during the index hospital admission, and 3 occurred in the post-discharge period. Subset analysis demonstrated that 4 (80%) fractures had occurred during the initial learning curve period, within the first 30 surgical cases with a SS. CONCLUSION/CONCLUSIONS:Short-stem hip prostheses are a safe alternative for THA. The results of the present study demonstrate a fracture incidence of 2.9% among patients. However, surgeons should remain cautious when utilizing new implant system and expect a learning curve. In this study, 80% of periprosthetic fractures following SS THA occurred within the first 30 cases for experienced arthroplasty-trained surgeons.

Total joint arthroplasty of the hip and knee are successful orthopedic procedures that reduce pain and improve mobility in patients. As the implanted materials used in these procedures have improved, the lifetime of the implants has now reached more than 20 years. Younger patients are undergoing total joint arthroplasty at increasing rates, which has increased the need for improvements in materials for extended implant longevity. In this review, we aim to provide historical perspective on the evolution of ultra-high-molecular-weight polyethylene in total joint arthroplasty. We review this material with respect to its structure, mechanical properties, wear rates, sterilization effects, crosslinking, and other new polymer innovations. Ultra-high-molecular-weight polyethylene (UHMWPE) has been a cornerstone for total joint arthroplasty and with continued design improvements will continue to be vital to this successful orthopedic operation.

With the aging population and rising incidence of primary total joint arthroplasty has come the increasing incidence of revision total hip arthroplasties. One challenge in revision total hip arthroplasty is dealing with acetabular defects. The orthopaedic surgeon who chooses to take on these challenges requires a proper method for the evaluation of these defects as well as an evidence-based treatment algorithm. Initial assessment requires appropriate use and interpretation of imaging modalities such as x-rays and computed tomography. Preoperative planning presupposes knowledge of available approaches and implant options, such as porous coated jumbo cups, modular augments, and cup-cage constructs. Surgical execution necessitates experience in the indications for each type of implant for various types of defects. This review will aid in the understanding of each step of the diagnosis and treatment of acetabular defects in revision total hip arthroplasty.