Good Short-Term Survivorship of Constrained Condylar Revision Knee Implants With Medial Pivot Kinematics: A Level IV Retrospective Study.

BACKGROUND: The need for revision total knee arthroplasty surgery is increasing worldwide, and, in many cases, a constrained implant is required to provide joint stability. The purpose of this study was to examine the early loosening and functional outcome of a novel constrained condylar (CCK) revision total knee system designed to have medial pivot (MP) kinematics. METHODS: A retrospective cohort study was performed, collecting clinical data from all patients who underwent revision total knee arthroplasty using a novel MP CCK system with a minimum four-year clinical follow-up. Patient demographics, survivorship, complications, and Forgotten Joint Score were analyzed based upon chart review. RESULTS: There were 49 patients available for follow-up, who had a 100% survivorship free of aseptic loosening. All-cause revision survivorship was 92%. There were 4 patients who subsequently underwent rerevision. The causes for rerevision included periprosthetic joint infection in 2 patients, coronal plane instability in one patient, and a traumatic knee dislocation in one patient. There were 45 patients who completed the Forgotten Joint Score, who had an average of 49.8 (± 32.8, range 6.25 to 100). CONCLUSIONS: At 4 years, mid-term follow-up, this novel CCK revision total knee system designed to have MP kinematics had good patient-reported outcomes with no revision for aseptic loosening. Future studies should evaluate the mid- and long-term survivorship of this innovative implant.

Total Knee Arthroplasty Periprosthetic Joint Infection With Concomitant Extensor Mechanism Disruption and Soft-Tissue Defect: The Knee Arthroplasty Terrible Triad.

BACKGROUND: Periprosthetic infection (PJI) with concomitant extensor mechanism disruption (EMD) and soft-tissue defect-hereinafter termed the "Terrible Triad"-is a devastating complication following total knee arthroplasty. The purpose of this study was to define the surgical and clinical outcomes following management of a cohort of patients who have the Terrible Triad. METHODS: From 2000 to 2022, 127 patients underwent operative management for PJI alone, 25 for PJI with soft-tissue defects (defined as defects requiring flap reconstruction or being a factor contributing to the decision of performing above-knee amputation or arthrodesis), 14 for PJI with EMD, and 22 for the Terrible Triad. A composite outcome of infection status, range of motion, extensor lag, and ambulatory status at final follow-up was used to compare the proportion of patients in each group with a favorable overall knee outcome. Differences between groups were determined using one-way analyses of variance with post hoc Tukey's tests and Pearson's Chi-square tests or Fisher's exact tests with post hoc Bonferroni adjustments, where applicable. Odds ratios (OR) were calculated for comparison of the overall knee outcome between groups. A Kaplan-Meier survival analysis for patient mortality was performed. RESULTS: The mean follow-up was 8.4 years and similar between groups (P = .064). Patients who had the Terrible Triad had a 45.5% incidence of above-knee amputation, or arthrodesis, and an 86.4% incidence of an unfavorable outcome. Compared to patients in the PJI group, patients in the PJI who had a soft-tissue defect (OR = 5.8, 95% CI [confidence interval] 2.2 to 15.7), PJI with EMD (OR = 3.7, 95%CI 1.0 to 12.9), and Terrible Triad groups (OR = 11.6, 95% CI 3.3 to 41.5) showed higher odds of an unfavorable knee outcome. CONCLUSIONS: This study demonstrates that the total knee arthroplasty Terrible Triad is a dreaded diagnosis with poor outcomes. Clinicians and patients might consider early treatment with amputation or arthrodesis. LEVEL OF EVIDENCE: III.

Clinical applications of augmented reality in orthopaedic surgery: a comprehensive narrative review.

PURPOSE: The development of augmented reality (AR) technology allows orthopaedic surgeons to incorporate and visualize surgical data, assisting the execution of both routine and complex surgical operations. Uniquely, AR technology allows a surgeon to view the surgical field and superimpose peri-operative imaging, anatomical landmarks, navigation guidance, and more, all in one view without the need for conjugate gaze between multiple screens. The aim of this literature review was to introduce the fundamental requirements for an augmented reality system and to assess the current applications, outcomes, and potential limitations to this technology. METHODS: A literature search was performed using MEDLINE and Embase databases, by two independent reviewers, who then collaboratively synthesized and collated the results of the literature search into a narrative review focused on the applications of augmented reality in major orthopaedic sub-specialties. RESULTS: Current technology requires that pre-operative patient data be acquired, and AR-compatible models constructed. Intra-operatively, to produce manipulatable virtual images into the user's view in real time, four major components are required including a camera, computer image processing technology, tracking tools, and an output screen. The user is provided with a heads-up display, which is a transparent display, enabling the user to look at both their natural view and the computer-generated images. Currently, high-quality evidence for clinical implementation of AR technology in the orthopaedic surgery operating room is lacking; however, growing in vitro literature highlights a multitude of potential applications, including increasing operative accuracy, improved biomechanical angular and alignment parameters, and potentially reduced operative time. CONCLUSION: While the application of AR systems in surgery is currently in its infancy, we anticipate rapid and widespread implementation of this technology in various orthopaedic sub-specialties.

Quality indicators in primary elective total hip and knee arthroplasty.

PURPOSE: Total hip arthroplasty (THA) and total knee arthroplasty (TKA) represent a significant portion of healthcare spending and are high-priority for quality improvement initiatives. This study aims to develop quality indicators (QIs) in the care of primary elective THA and TKA patients. These QIs serve a number of purposes including documentation of the quality of care, objective comparisons of institutions/providers, facilitating pay-for-performance initiatives, and supporting accountability, regulation, and accreditation. METHODS: A guideline-based approach, initially described by Kötter et al., was utilized. Eight clinical practice guidelines (CPGs) were evaluated for candidate indicators (CIs). CIs with high-quality evidence and consensus statements were extracted. Eighteen additional CIs were included from previous work that evaluated quality improvement databases. Each CI and supporting evidence was submitted for independent review by an expert panel. The RAND Corporation-University of California, Los Angeles (RAND/UCLA) appropriateness methodology was utilized and items were rated based on validity, reliability, and feasibility of measurement. After two rounds of ratings and ranking, a final ranked list of QIs was obtained. RESULTS: Fifty-six CIs were identified from the literature and CPGs or proposed by the expert panel. Two rounds of voting resulted in 12 total QIs that were deemed appropriate measures of high-quality care. The final 12 QIs were ranked by order of importance: use of peri-operative tranexamic acid, infusion of prophylactic antibiotics prior to inflation of tourniquet, appropriate post-operative venous thromboembolic prophylaxis, complication rate, rate of secondary procedure, readmission rate, early mobilization, average change of pre- to one year post-operative functional status, use of multimodal analgesia, use of neuraxial anesthesia, use of peri-articular injection in TKA, and use of pre-operative PO analgesia. CONCLUSION: This study is an expert opinion based on parameters observed in modern and high-quality academic settings. Twelve QIs are proposed to assess the quality of care in the peri-operative management of primary elective THA and TKA patients.

Long-term outcomes of the Nexgen© posterior stabilized knee: minimum 15 year follow-safe and effective.

PURPOSE: Studying long-term survivorship and functional outcomes for specific prostheses is critical for elucidating areas in need of design improvement. This study reports the long-term of the NexGen Posterior Stabilized (PS) Total Knee implant (TKA) (Zimmer Biomet, Warsaw IN) Performed by a single surgeon. METHODS: Data from patients treated with the NexGen PS TKA between January 2003 and December 2005 with a minimal follow-up of 15 years was collected from a prospectively collected database. Survivorship rates and Oxford Knee Scores (OKS) were obtained for those patients available for follow-up. RESULTS: Ninety-five patients met the inclusion criteria during the study period. OKS was available for 44 (46%) patients. Ten patients required revision surgery (10.52%). Implant-specific survivorship of all cases that were reviewed was 98%. Survivorship of implants in patients that we were able to reach, or deceased patients was 93%. The average Oxford Knee Score was 39.1 (14-48. SD ± 7.70) with 48 being the maximal score. CONCLUSION: Despite some concerns about durability of this implant, good longevity and function was demonstrated. At a minimum of 15 years follow-up in this cohort. Given these results design features of this system should be considered for future generations of implants.

Comparing Analgesia on an As-Needed Basis to Traditional Intravenous Patient-Controlled Analgesia Within Fast-Track Orthopedic Procedures: A Randomized Controlled Trial.

BACKGROUND: The aim was to determine if the use of intravenous patient-controlled analgesia (IVPCA) in a fast-track joint replacement program is associated with increased use of perioperative opioid consumption and increased length of hospital stay. DESIGN: A prospective, double-blind, randomized controlled trial. SETTINGS: Academic hospital. PARTICIPANTS/SUBJECTS: A total of 80 patients aged 18-85 years, with body mass index (BMI) 18-40, undergoing elective total knee arthroplasty were recruited. METHODS: Pre-operatively, patients received gabapentin, celecoxib, and acetaminophen. Peri-operatively, patients received spinal anesthesia with morphine and fentanyl, and periarticular local anesthetic administration by the surgeon. Postoperatively, 80 patients were randomized by a computer-generated sequence into IVPCA group (group A, n = 40) and non-IVPCA group (group B, n = 40). RESULTS: The primary outcome was 48-hour postoperative opioid consumption and length of hospital stay. Secondary outcomes included side effects of opioids, patient satisfaction, and pain scores. There was no significant difference within 48-hour postoperative opioid consumption (median 61.3 vs. 87.5, p = .181) and length of hospital stay (median 49.8 hours vs. 49.5 hours; p = .89) between the two groups. Also, there was no significant difference in patient satisfaction (median 5 in both groups), pain scores, and opioid-related side effects. CONCLUSIONS: IVPCA was associated with nonsignificant reduction in opioid exposure in elective total knee arthroplasty surgery within 48 hours. Neither group was superior in terms of length of hospital stay, opioid related side-effects, pain scores, and patient satisfaction.

Superior patient satisfaction in medial pivot as compared to posterior stabilized total knee arthroplasty: a prospective randomized study.

PURPOSE: Medial pivot (MP) total knee arthroplasty (TKA) aims to restore native knee kinematics due to highly conforming medial tibio-femoral articulation with survival comparable to contemporary knee designs. Posterior stabilized (PS) TKAs use cam-post mechanism to restore native femoral rollback. However, there is conflicting evidence regarding the reported patient satisfaction with MP TKA designs when compared to PS TKAs. The primary aim of this study is to compare the patient satisfaction between MP and PS TKA and the secondary aim is to establish potential reasons behind any differences in the outcomes noted between these two design philosophies. METHODS: In this IRB-approved single surgeon, single centre prospective RCT, 53 patients (mean age 62 years, 42 women) with comparable bilateral end-stage knee arthritis undergoing simultaneous bilateral TKA were randomized to receive MP TKA in one knee and PS TKA in the contralateral knee. At 4 years post-surgery, all patients were assessed using Knee Society Score (KSS)-Satisfaction and -Expectation scores, and Oxford Knee Score (OKS). In addition, all the patients underwent standardized radiological and in vivo kinematic assessment. RESULTS: Patients were more satisfied with the MP TKA as compared to PS TKA: mean KSS-Satisfaction [34.5 ± 3.05 in MP and 31.7 ± 3.16 in PS TKAs (p < 0.0001)] and mean KSS-Expectation scores [12.5 ± 1.39 in MP TKAs and 11.2 ± 1.41 in PS TKAs (p < 0.0001)]. No significant difference was noted in any other clinical outcomes. The in vivo kinematics of MP TKAs was significantly better than those of PS TKAs. CONCLUSION: MP TKAs provide superior patient satisfaction and patient expectations as compared to PS TKA. This may be related to better replication of natural knee kinematics with MP TKA. LEVEL OF EVIDENCE: I.

Reducing Acute Hospitalization Length of Stay After Total Knee Arthroplasty: A Quality Improvement Study.

BACKGROUND: The introduction of bundled funding for total knee arthroplasty (TKA) has motivated hospitals to improve quality of care while minimizing costs. The aim of our quality improvement project is to reduce the acute hospitalization length of stay to less than 2 days and decrease the percentage of TKA patients discharged to inpatient rehabilitation using an enhanced recovery after surgery bundle. METHODS: This study used a before-and-after design. The pre-intervention period was January to December 2017 and the post-intervention period was January 2018 to August 2019. A root cause analysis was performed by a multidisciplinary team to identify barriers for rapid recovery and discharge. Four new interventions were chosen as part of an improvement bundle based on existing local practices, literature review, and feasibility analysis: (1) perioperative peripheral nerve block; (2) prophylactic antiemetic medication; (3) avoidance of routine preoperative urinary catheterization; and (4) preoperative patient education. RESULTS: The pre-intervention and post-intervention groups included 232 and 383 patients, respectively. Mean length of stay decreased from 2.82 to 2.13 days (P < .001). The need for inpatient rehabilitation decreased from 20.2% to 10.7% (P = .002). Mean 24-hour oral morphine consumption decreased from 60 to 38 mg (P < .001). The percentage of patients experiencing moderate-to-severe pain and postoperative nausea and vomiting within the first 24 hours decreased by 25% and 15%, respectively (P < .001). Thirty-day emergency department visits following discharge decreased from 12.9% to 7.3% (P = .030). CONCLUSION: Significant improvements in the recovery of patients after TKA were achieved by performing a root cause analysis and implementing a multidisciplinary, patient-centered enhanced recovery after surgery bundle. LEVEL OF EVIDENCE: Level III.

Evaluation of the Medial Stabilized Knee Design Using Data From National Joint Registries and Current Literature.

BACKGROUND: Various designs of total knee arthroplasty (TKA) have provided satisfactory outcomes for the treatment of knee osteoarthritis for many years. The aim of the study is to evaluate the success and failure rate of the medial stabilized (MS) TKA design through national joint registries and the current literature. MATERIALS AND METHODS: A comprehensive literature review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses was carried out through PubMed and MEDLINE database. The international registries analyzed included the National Joint Registry, the Australian Orthopedic Association National Joint Replacement Registry, the Dutch Arthroplasty Register, the New Zealand Orthopedic Association Joint Registry, and the Michigan Arthroplasty Registry Collaborative Quality Initiative. We are reporting descriptive data which include means and percentages of survival rates and revision rates and number of years after the primary procedure. The revision rates and the cumulative revision rates are reported separately for each MS implant. RESULTS: Our detailed review identified 5 of 12 registries and 25 of 550 studies reporting on the survivorship of an MS TKA design. There were a total of 3684 procedures between the 25 studies, with an average survivorship free of aseptic loosening of 99% at 6.9 years. There are 26,693 (2.5%) MS TKAs in the current National Joint Registry with a mean cumulative revision rate of 2.63% at 5 years, 3.35% at 10 years, and 4.6% at 15 years. The Australian Orthopedic Association National Joint Replacement Registry provides survivorship data on 19,249 (2.9%) MS TKAs, with a mean cumulative revision rate of 3.34% at 5 years, 7.4% at 10 years, and 8.1% at 15 years. The Dutch Arthroplasty Register contains survivorship data on 1490 MS designs and a mean revision rate of these implants is 0.8% at 1 year, 5.95% at 5 years, and 9.8% at 10 years. The Evolution MP is the only implant reported in the Michigan Arthroplasty Registry Collaborative Quality Initiative and has a revision rate of 2.28% at 3 years. CONCLUSION: The MS TKA design has comparable results to traditional TKA designs across several joint registries and 25 studies in the literature.

The Effect of Polyethylene Liner Thickness on Patient Outcomes and Failure After Primary Total Knee Arthroplasty.

BACKGROUND: The effect of using thicker liners in primary total knee arthroplasty (TKA) on functional outcomes and aseptic failure rates remains largely unknown. As such, we devised a multicenter study to assess both the clinical outcomes and survivorship of thick vs thin liners after primary TKA. METHODS: A search of our institutional databases was performed for patients having undergone bilateral (simultaneous or staged) primary TKA with similar preoperative and surgical characteristics between both sides. Two cohorts were created: thick liners and thin liners. Outcomes collected were as follows: change in Knee Society Score (ΔKSS), change in range of motion, and aseptic revision. Ad hoc power analysis was performed for ΔKSS (⍺ = 0.05; power = 80%). Differences between cohorts were assessed. RESULTS: About 195 TKAs were identified for each cohort. ΔKSS and change in range of motion in the thin vs thick cohorts were similar: 51.4 vs 51.6 (P = .86) and 11.1° vs 10.0° (P = .66), respectively. No difference in aseptic revision rates were observed between thin and thick cohorts: all cause (4.1%, 3.1%; P = .59), aseptic loosening (0.5%, 0.5%; P = 1.0), instability (0.5%, 0.5%; P = 1.0), all-cause revision for stiffness (3.1%, 2.1%; P = .52), manipulation under anesthesia (2.1%, 2.1%; P = 1.0), and liner exchange (0.5%, 0%; P = .32). CONCLUSION: The results of this study suggest that both rates of revision surgery and clinical outcomes are similar for TKAs performed with thick and thin liners. Preoperative factors are likely to play an important role in liner thickness selection, and emphasis should be placed on ensuring sound surgical technique.

Revision total knee arthroplasty for patellar dislocation in patients with malrotated TKA components.

PURPOSE: Patellar dislocation is a serious complication leading to patient morbidity following total knee arthroplasty (TKA). The cause can be multifactorial. Extensor mechanism imbalance may be present and result from technical errors such as malrotation of the implants. We sought to understand the reasons for post-arthroplasty patellar dislocation and the clinical outcomes of patients in whom it occurs. METHODS: This is a retrospective cohort study assessing the outcomes of revision surgery for patellar dislocation in patients with component malrotation in both primary and revision TKAs. Patient demographics, dislocation etiology, presurgical deformity, intraoperation component position, complications, reoperation, and Knee Society Scores (KSS) were collected. RESULTS: Twenty patients (21 knees) were identified. The average time from primary arthroplasty to onset of dislocation was 33.6 months (SD 44.4), and the average time from dislocation to revision was 3.38 months (SD 2.81). Seventeen knees (80.9%) had internal rotation of the tibial component and seven knees (33.3%) had combined internal rotation of both the femoral and tibial components. Fifteen knees (71.4%) were treated with a condylar constrained implant at the time of revision, and five knees were converted to a hinged prosthesis. The average follow-up time was 56 months. During this time, one patient (4.54%) had a recurrent dislocation episode, requiring further surgery. At final follow up, the mean KSS was 86.2. CONCLUSION: Revision TKA following patellar dislocation for patients with malrotated components was associated with high success rates. After revision surgery, patients had a low recurrence of patellar dislocation, low complication rates, and excellent functional outcomes.

Rotating hinge knee causes lower bone-implant interface stress compared to constrained condylar knee replacement.

PURPOSE: To compare the stresses at bone-arthroplasty interface of constrained and semi-constrained knee prostheses, using the finite element (FE) method as a predictor of the survivorship of the implants. METHODS: Three-dimensional FE models of the knee implanted with rotating hinge (RHK) and legacy constrained condylar (LCCK) prostheses were generated to study the loads and stresses for two situations: medial- and lateral collateral ligament deficiencies in full extension. RESULTS: On average, the shear stress developed at bone-implant interface dropped from 16.9 to 13.7 MPa (18.9%), and the interface von Mises stress lowered from 37.6 to 30.2 MPa (19.6%) in RHK compared to those in LCCK prostheses. RHK design also resulted in a more uniform stress distribution at the interfaces in both femur and tibia. The average polyethylene liner stress dropped from 9.6 to 2.6 MPa (a 72.7% decrease) in RHK design when compared to that in LCCK design. CONCLUSION: The more uniform interface stress suggests fewer density changes at the periprosthetic regions due to bone remodelling. Moreover, the lower polyethylene stresses are likely to reduce wear and damage. These findings reveal that the RHK design may have more favorable mechanical features compared to LCCK design in full extension boundary conditions, implying a potentially better survivorship. However, the findings should be interpreted cautiously as other configurations were not investigated.

The Effectiveness of Repeat Two-Stage Revision for the Treatment of Recalcitrant Total Knee Arthroplasty Infection.

BACKGROUND: The gold-standard method in North America for the management of infected total knee arthroplasty is 2-stage revision arthroplasty. This has provided generally a high success rate. However, persistent infection after 2-stage revision knee arthroplasty does occur. The purpose of this study was to predict the success rate of second, 2-stage revision arthroplasty. METHODS: All infected total knee arthroplasty treated between 2000 and 2015 that were operated by a single senior surgeon were reviewed retrospectively. Patients were stratified according to general health and limb status according to the Musculoskeletal Infection Society (MSIS) scoring system. The reinfection rate at the last follow-up was identified. The chi-square test and Fisher exact test were used to compare binary variables. RESULTS: We found a statistical relationship between the higher stage of MSIS score, type of microorganism, flap surgery, and reinfection rate after reimplantation of second two-stage surgery. There is not any statistically significant correlation between age, gender, constraint pattern of prosthesis, number of spacers, and time interval between the first and second stages of second 2-stage surgery with the numbers available in this study. CONCLUSION: Another 2-stage knee revision is an effective method of treatment. However, we found a higher incidence of failure in those patients with poor general health based on the MSIS score, inadequate soft tissue envelope and resistant bacteria. The success of second, 2-stage protocol is best in patients with optimized general health, soft tissue coverage, and antibiotic-sensitive microorganism. Patients who cannot be optimized are most likely to require amputation or knee arthrodesis than another futile 2-stage surgery.

Patient willingness to contribute to the cost of novel implants in total joint arthroplasty: the Canadian experience

Background: In Canada, health care is covered by provincial health insurance programs; patients do not directly participate in paying for their acute care expenses. The aim of this study is to assess the willingness of Canadian patients to contribute to the costs of novel total joint arthroplasty implants. Methods: We administered a questionnaire to patients attending an outpatient arthroplasty clinic in Ontario. In the questionnaire, the longevity and risk of complications of a "standard" implant were described. We asked if participants would be willing to contribute to the cost of 3 novel implants that had differing longevities and risks of complications compared with the standard implant. Results: One hundred and fifteen patients completed our questionnaire. Up to 62% of patients were willing to contribute a copayment to get an implant with greater longevity. Willingness to pay decreased to 40% for an implant with greater longevity but an increased risk of complications. Forty percent of participants were willing to pay for an implant with the same longevity as the standard implant but a decreased risk of complications. Participants with a higher income were more willing than other participants to contribute to the cost of a novel implant with greater longevity or lower complication rates. Conclusion: This study demonstrated that up to 62% of our sample of patients in Ontario were willing to share the costs of a novel total joint replacement implant. Willingness to pay was associated with the proposed benefits of the implant and certain patient characteristics. Our study shows that a high proportion of Canadian patients may be willing to copay to have access to new technologies.

Contexte: Au Canada, les soins de santé sont assurés par les régimes provinciaux d'assurance maladie; les patients ne participent pas directement au paiement des soins de santé actifs. Le but de cette étude était de vérifier si les patients canadiens sont prêts à contribuer au paiement de prothèses d'un type nouveau pour les arthroplasties totales. Méthodes: Nous avons administré un questionnaire à des patients d'une clinique externe d'arthroplastie en Ontario. Dans le questionnaire, on décrivait la durée de vie et les risques de complications associés à une prothèse « standard ¼. Nous avons demandé aux participants s'ils étaient ouverts à l'idée de contribuer au paiement de 3 prothèses d'un nouveau type, comportant une durée de vie et des risques de complications différents de ceux de la prothèse standard. Résultats: Cent quinze patients ont répondu à notre questionnaire. Jusqu'à 62 % des patients se sont dits prêts à contribuer à une forme de copaiement pour obtenir une prothèse plus durable. La volonté de payer diminuait à 40 % pour une prothèse plus durable mais comportant plus de risques de complications. Quarante pour cent des participants se sont dits prêts à payer pour une prothèse de même durée de vie que la prothèse standard, mais comportant moins de risques de complications. Les participants ayant un revenu plus élevé étaient davantage disposés à contribuer au paiement d'une prothèse d'un nouveau type plus durable et comportant moins de risques de complications comparativement aux autres participants. Conclusion: Cette étude a démontré que jusqu'à 62 % de notre échantillon de patients ontariens étaient prêts à partager les coûts d'une nouvelle prothèse pour arthroplastie totale. La volonté de payer était associée aux avantages présumés de la prothèse et à certaines caractéristiques des patients. Notre étude montre qu'une forte proportion de patients canadiens seraient prêts à s'engager dans un copaiement pour avoir accès à de nouvelles technologies.

A Retrospective Comparison of a Medial Pivot and Posterior-Stabilized Total Knee Arthroplasty With Respect to Patient-Reported and Radiographic Outcomes.

BACKGROUND: Medial pivot (MP) type total knee arthroplasty (TKA) implants are designed with a highly congruent medial tibiofemoral articulation. Compared with the cam-and-post design of the posterior-stabilized (PS) TKA, the MP-TKA design has been hypothesized to better replicate the natural kinematics of the knee. We compared the MP-TKA and PS-TKA designs, with our primary outcome measures being range of motion (ROM) and patient-reported satisfaction. METHODS: This study was a retrospective comparison between the 2 groups (76 MP-TKA vs 88 PS-TKA). ROM was collected preoperatively, 6 weeks, 6 months, and 1 year postoperatively. The Forgotten Joint Score-12 (FJS-12) scores were collected at a minimum of 1 year postoperatively. RESULTS: There was no statistically significant difference in age, gender, or body mass index between the groups. We found a statistical difference in preoperative ROM (MP = 120.3°, PS = 112.8°, P = .002). There was no difference in ΔROM at 6 weeks (MP = -12.36, PS = -3.79, P = .066), 6 months (MP = -4.23, PS = 2.73, P = .182), or 1 year (MP = .17, PS = 3.31, P = .499). Patients who underwent the MP-TKA scored significantly better than the PS-TKA on the FJS-12 score (MP = 59.72, PS = 44.77, P = .007). CONCLUSION: We found that patients who underwent the MP-TKA scored better on the FJS than those who underwent the PS-TKA; particularly with regard to deep knee flexion and stability of the prosthesis. The MP-TKA design may offer improved patient outcomes because of its highly congruent medial tibiofemoral articulation.

The medial border of the tibial tuberosity as an auxiliary tool for tibial component rotational alignment during total knee arthroplasty (TKA).

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° (range 15°-24°) vs. 20.7° (range 16°-25°), respectively]. In 89.3 % of the patients, the angle ranged from 17° to 24°. No statistical difference (p n.s.) was found between women and men in both normal [median -20.7° (range 16°-25°) vs. 19.9° (range 15°-24°)] and post-TKA tibiae [median 21.4° (range 19°-24°) vs. 20° (range 16°-25°)]. CONCLUSION: This study found that in 90 % of the patients, the medial border of the tibial tuberosity is internally rotated 17°-24° 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.

Patient's Height and Hip Medial Offset Are the Main Determinants of the Valgus Cut Angle During Total Knee Arthroplasty.

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° (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.

The results of two-stage revision TKA using Ceftazidime-Vancomycin-impregnated cement articulating spacers in Tsukayama Type II periprosthetic joint infections.

PURPOSE: This study examined the success and factors associated with failure, of using cement spacers impregnated with high-dose Ceftazidime and Vancomycin when performing two-stage revision for infected total knee arthroplasty (TKA). METHODS: A retrospective analysis was performed using a prospectively collected database of 82 patients (median age 68 years, range 39-87) with a confirmed deep TKA infection treated with a two-stage revision. All cement spacers were impregnated with high-dose Ceftazidime and Vancomycin. The rate of success was recorded-an association between failure of treatment, and patient factors, previous surgical treatment, and microbial characteristics was sought. RESULTS: The mean time to infection from index arthroplasty was 45 months (range 3-240). The initial two-stage revision was successful in 70/82 patients (85.4 %), who remained free of infection at average follow-up of 36.2 months (range 24-85). A second two-stage revision for infection was required in 12/82 patients (14.6 %), which was successful in 4/12 (33 %). A third two-stage revision was performed in three patients, all of whom had a polymicrobial infection of which only one patient had successful eradication of infection. Recurrent infection was correlated with irrigation and debridement with implant retention prior to initial two-stage revision (p < 0.01), polymicrobial infections (p = 0.035), and infections presenting <6 months after index surgery (p = 0.031). No correlation was seen with age, BMI, type of organism, diabetes mellitus, or Charlson Comorbidity Index. CONCLUSION: The findings of this study suggest that the combination of Ceftazidime and Vancomycin in cement spacers is as efficacious as other published single or combined antibiotic mixtures, which is clinically relevant to clinicians treating this difficult problem in the setting of patients with compromised renal function.

Distal Femoral Arthroplasty for Management of Periprosthetic Supracondylar Fractures of the Femur.

BACKROUND: The incidence of periprosthetic supracondylar femoral fractures is 0.3% to 2.5% after primary total knee arthroplasty. METHODS: We performed a retrospective review 17 patients managed by distal femoral arthroplasty for periprosthetic supracondylar femoral fracture. RESULTS: Mean age was 76 years (SD, 12.58). Mean follow-up was 33.9 months (SD, 10.57). Mean final range of motion was 2° of fixed flexion (SD, 5.3) and flexion of 90.2° (SD, 20.8). Mean final follow-up Knee Society Score was 67.15 (SD, 19.7). Mean Short Form-12 physical component was 36.57 (SD, 11.2), and mean Short Form-12 mental component was 42.64 (SD, 12.09). Four complications (4 patients) were managed successfully without revision of the prosthesis. Two failures (2 patients) required prosthesis revision: patellar maltracking with knee dislocation, and periprosthetric femoral fracture. CONCLUSION: Distal femoral arthroplasty is a successful procedure. Complication rates are not insignificant, which is expected with the complexity of this clinical scenario.