Do Stemmed Tibial Components in Total Knee Arthroplasty Improve Outcomes in Patients With Obesity?

Biomechanical Effects of Stem Extension of Tibial Components for Medial Tibial Bone Defects in Total Knee Arthroplasty: A Finite Element Study

The aim of this study was to investigate the biomechanical effects of stem extension with a medial tibial bone defect in primary total knee arthroplasty (TKA) on load distribution and stress in the proximal tibia using finite element (FE) analysis.FE simulations were performed on the tibia bone to evaluate the stress and strain on the tibia bone and bone cement. This was done to investigate the stress shielding effect, stability of the tibia plate, and the biomechanical effects in TKA models with various medial defects and different stem length models.The results demonstrated that in the bone defect model, the longer the stem, the lower the average von Mises stress on the cortical and trabecular bones. In particular, as the bone defect increased, the average von Mises stress on cortical and trabecular bones increased. The average increase in stress according to the size of the bone defect was smaller in the long stem than in the short stem. The maximal principal strain on the trabecular bone occurred mainly at the contact point on the distal end of the stem of the tibial implant. When a short stem was applied, the maximal principal strain on the trabecular bone was approximately 8% and 20% smaller than when a long stem was applied or when no stem was applied, respectively.The findings suggest that a short stem extension of the tibial component could help achieve excellent biomechanical results when performing TKA with a medial tibial bone defect.

Exploring consistent ratios in morphometry of the proximal tibia: insights for knee arthroplasty

INTRODUCTION

The current study, which delves into proximal tibia morphometric parameters in a Greek sample, not only analyzes whether specific linear distance ratios are consistent but also paves the way for a potential novel metric system for knee arthroplasty imaging studies using constant ratios. These findings could have significant implications for future enlarged research and clinical practice.

METHODS

A total of 38 dried tibiae were evaluated by two independent investigators. The following distances were measured with a digital Vernier sliding caliper: (1) the mediolateral distance of the proximal surface (A), (2) the anteroposterior distance of the proximal surface (B), (3) The longitudinal length of the bone (C), (4) the line connecting the anterior margin of the proximal surface with the highest peak of the tibia tuberosity (D), (5) the depth of the proximal margin of the medial articular facet (AF) (medial plateau) (E) and (6) the depth of the proximal margin of the lateral AF (lateral plateau) (F).

RESULTS

The A, B, C, D, E, and F mean distances were 71.3 mm, 47.4 mm, 340.2 mm, 37.1 mm, 42 mm, and 35.9 mm. Reliability analysis for each observer on all measurements revealed an interclass correlation (ICC) score of 0.975 (observer 1) and 0.971 (observer 2). The ratio A/B was 1.5, A/C was a constant 0.2, and D/C was 0.1. The ratio E/F was 1.2. The six measurements (A-F) showed excellent inter-observer reliability (all ICC values > 0.990).

CONCLUSIONS

The study established constant ratios of the studied linear distances around the proximal tibia. Considering these ratios, asymmetrical tibial components in knee arthroplasty seem to replicate the native anatomy more closely. Furthermore, the distance from the anterior margin of the proximal surface to the tibial tuberosity peak, constituting one-tenth of the longitudinal length of the tibia, shows promise as a metric system for imaging studies, especially in assessing lesions around tibial components.

The use of a tibial stem in primary total knee arthroplasty for patients with a frontal deformity of more than ten degrees reduces the rate of postoperative pain

BACKGROUND

The use of a tibial stem for large deformities (> 10°) would reduce the incidence of pain. The aim of this study was to compare the effect of tibial stem on postoperative pain and aseptic loosening at the tibia in patients with a preoperative deformity > 10° in the frontal plane at 2 years follow-up.

METHODS

This was a retrospective single-center case-control study. Ninety-eight patients with deformities greater than 10° in the frontal plane and a BMI > 30 kg/m2 who had undergone posterior-stabilized (PS) total knee arthroplasty (TKA) with a tibial stem were matched using a propensity score to 98 patients who had undergone PS TKA without a tibial stem. The primary endpoint was the pain rate at 2 years. The secondary endpoints were the rate of aseptic loosening of the tibia at 2 years post-operatively.

RESULTS

A significant difference was found in the rate of postoperative pain at 2 years. It was higher in the group without tibial stem compared with the group with tibial stem (41.8% vs 17.3%, p = 0.0003). In the group without tibial stem, 24.4% of pain was mild, 61% moderate and no severe pain. In the tibial stem group, 47.1% of pain was mild, 41.2% moderate and no severe pain. A radiolucent line (RLL) was present at 2 years in 26.5% of prostheses in the without tibial stem group and in 9.2% of prostheses in the tibial stem group (p = 0.002). There was no difference between the two groups in terms of aseptic loosening.

CONCLUSION

The use of a tibial stem in primary TKA in patients with frontal deformities greater than 10° reduces postoperative pain and the presence of radiolucent lines.

Outcomes of Short and Long Tibial Stems for Primary Total Knee Arthroplasty in a Population of Obese Patients at Two-Year Follow-Up: A Clinical and Biomechanical Study

BACKGROUND

Obesity can be a source of higher failure rates and inferior clinical outcomes after total knee arthroplasty (TKA). The aim of this study was to compare outcomes, failure rates, and stress distributions of TKA in obese patients using a short, long, or no tibial stem.

METHODS

A matching process based on the type of stem used and the age allowed included 180 patients who had a body mass index (BMI) > 30 and underwent a TKA between January 2010 and December 2019, with a minimum follow-up of 2 years. They were classified as moderately obese (MO: 30 < BMI < 35, N = 90) and severely obese (SO: BMI > 35, N = 90). For each, 3 subgroups were defined: thirty patients received a 30 mm short stem (SS), thirty received a 100 mm long stem (LS), and thirty received no stem (NS). Patients were assessed preoperatively and postoperatively using the Knee Society Score (KSS). A finite element model was developed to evaluate the biomechanical effects of the tibial stem on stress distribution in the subchondral bone based on BMI.

RESULTS

The SS patients had significantly higher postoperative KSS knee score [MO: 88.9 (SS) versus 79 (LS) versus 80.6 (NS); SO: 84.5 versus 72.4 versus 78.2] (P < .0001) and function score [MO: 90.4 (SS) versus 78.4 (LS) versus 68.5 (NS); SO: 85.5 versus 73 versus 61.8] (P < .0001) compared to LS and NS patients. The biomechanical study demonstrated a BMI-dependent increase in stress in the subchondral bone in contact with the tibial components. These stresses were mainly distributed at the tibial cut for NS and along the stem for SS and LS.

CONCLUSIONS

A short, cemented tibial stem offers better functional outcomes without increasing failure rates compared to a longer stem during primary TKA in a population of obese patients at two-year follow-up. A short tibial stem does not lead to increased stress compared to an LS, at least for certain BMI categories.

Current Evidence Does Not Support the Use of Tibial Stem Extension in Total Knee Arthroplasty of Obese Patients: A Systematic Review

BACKGROUND

Obesity rates have been increasing globally, leading to a higher incidence of knee osteoarthritis and a surge in primary and revision total knee arthroplasty (TKA). The debate continues on the impact of obesity on TKA success, particularly regarding the use of stemmed tibial components in obese patients. This systematic review aimed to compare the effectiveness of stemmed tibial components versus standard keeled tibial components in obese patients undergoing TKA.

METHODS

A systematic review was conducted using databases including PubMed, Embase, Scopus, and Web of Science from inception to December 2023. The eligibility criteria were Participants: Patients who have obesity undergoing TKA; Intervention: stemmed TKA; Comparator: standard keeled tibial TKA; Outcomes: aseptic loosening, patient-reported outcome measures (PROMs), and overall revision. Data extraction and quality assessment were performed using the Newcastle-Ottawa Scale for cohort studies and the Cochrane risk-of-bias tool for randomized trials.

RESULTS

The search yielded 470 studies, with 10 studies (42,533 knees) meeting the inclusion criteria. These studies included 3 randomized controlled trials and 7 retrospective cohorts. The primary outcomes measured were aseptic loosening and overall revision rates, while secondary outcomes included PROMs. Results indicated mixed findings, with some studies suggesting improved outcomes with stemmed components in cases of aseptic loosening and mechanical failure, while others showed no significant difference. The PROMs did not show a significant difference between groups post-TKA. The certainty of the evidence was graded as "very low" using the Grading of Recommendations, Assessment, Development, and Evaluations framework.

CONCLUSIONS

Current literature does not provide conclusive evidence to support the routine use of stemmed tibial components in TKA for obese patients. The decision to use stem extensions should not solely rely on the patient's obesity status. Further high-quality studies are needed to clarify the role of stemmed components in TKA for this patient population.

LEVEL OF EVIDENCE

III.

Comprehensive evaluation of risk factors for aseptic loosening in cemented total knee arthroplasty: A systematic review and meta-analysis

Purpose

Aseptic loosening is the most common cause for revisions after total knee arthroplasty (TKA). Despite many studies exploring various risk factors associated with aseptic loosening, findings often present inconsistencies. To address this, we conducted a thorough review of the literature to identify and analyse these risk factors in cemented TKA. Additionally, we performed a meta-analysis to reconcile the divergent conclusions observed across studies.

Methods

We searched PubMed, Web of Science and Embase from 1996 up to 2024 and evaluated the quality of the included literature. Seventy-four studies were included to assess the association of BMI, diabetes, high physical activity (HPA), osteoporosis, rheumatoid arthritis (RA), cement material and implant design. Twenty-nine studies were used to calculate relative risk and CIs (using the random effects theory) and study heterogeneity for six different risk factors (BMI, diabetes, HPA level, cement material, polyethylene and implant design).

Results

Patients with diabetes are eight times more likely to experience aseptic loosening compared to those without diabetes (RR = 9.18, 95% CI: 1.80-46.77, p < 0.01). The use of tibial stem extension or highly crosslinked polyethylene can help reduce the incidence of aseptic loosening. However, we did not identify BMI, HPA, osteoporosis, RA, the use of high-viscosity cement and the utilization of mobile-bearing designs as risk factors for aseptic loosening post-cemented TKA.

Conclusions

Patients with diabetes undergoing TKA should be counselled regarding their potential increased risk of aseptic loosening. The use of tibial stem extensions and HXLPE can mitigate the incidence of aseptic loosening in cemented TKA. However, given a limited number of studies were included in the meta-analysis, we believe that higher-level studies are necessary to clearly identify other risk factors.

Level of Evidence

Level III.

Utilizing Stems in Primary Total Knee Arthroplasty: Analysis of the Australian Orthopaedic Association National Joint Replacement Registry Data

BACKGROUND

We compared revision rates and reasons for revision for primary total knee arthroplasty (TKA) performed for osteoarthritis with and without tibial stem extensions.

METHODS

Data from the Australian Orthopaedic Association National Joint Replacement Registry were used to compare all-cause revision, reason, and type of revision between primary TKA using stemmed tibial prostheses and non-stemmed prostheses.

RESULTS

All-cause revision for TKA with stem extension was higher for the first 6 months (hazard ratio [HR] 1.47; 95% confidence interval [CI]1.19 to 1.82; P < .001); while after 1.5 years TKA with stem extension had a lower rate of revision (HR 0.84; 95% CI 0.73 to 0.97; P = .01). Stemmed components were more likely to be revised for infection between 3 months and 1.5 years after surgery (HR 1.39; 95% CI 1.05 to 1.83; P = .02). The revision rate for aseptic loosening was lower in the stemmed group beyond 2 years (HR = 0.45; 95% CI 0.31 to 0.63; P < .001). Insert-only revision was higher in the stemmed group at all times (HR = 1.42; 95% CI 1.21 to 1.66, P < .001). Isolated tibial component revision was lower in the stemmed group at all times (HR 0.47; 95% CI 0.29 to 0.74; P = .001). Aseptic loosening for tibial component-only revision was significantly lower in the stemmed group at all times (HR 0.23; 95% CI 0.11 to 0.50; P < .001).

CONCLUSIONS

Patients undergoing primary stemmed TKA have lower rates of all-cause revision beyond 1.5 years and tibial component-only revision at all times. Further investigation is required to preoperatively select patients that benefit from augmentation with stems.

Does the use of tibial stem extensions reduce the risk of aseptic loosening in obese patients undergoing primary total knee arthroplasty: A systematic review and meta-analysis

BACKGROUND

This study aimed to compare the risk of revision for aseptic loosening in obese (body mass index >30 kg/m2) patients with stemmed (ST) versus non-stemmed (NST) tibial implants in primary total knee arthroplasty (TKA).

METHODS

A systematic review and meta-analysis were conducted following PRISMA and MOOSE guidelines. Studies reporting a direct comparison between ST and NST tibial implants in obese patients were included. The primary outcome of interest was revision for aseptic loosening. Outcomes were analysed using meta-analysis of relative risk. Risk of bias assessment was performed using the Newcastle-Ottawa Scale for observational studies and the RoB-2 Cochrane tool for randomised studies.

RESULTS

Seven studies met the selection criteria, consisting of four cohort studies and three randomised controlled trials. Mean follow up time for the eligible cohort was 62.6 months. Meta-analysis demonstrated a statistically significant reduction in the risk of aseptic revision in the ST group compared with the NST group (risk ratio 0.25, 95% confidence interval 0.07 to 0.92). After removal of all zero-event studies, the results remained in favour of the ST group (risk ratio 0.15, 95% confidence interval 0.03 to 0.64).

CONCLUSIONS

This study found that obese patients undergoing TKA with stemmed tibial implants may have a lower risk of aseptic revision compared with those with non-stemmed tibial implants. However, due to the lack of high-quality literature available, our study is unable to draw a definitive conclusion on this matter. We suggest that this topic should be re-evaluated using higher-quality study methods, particularly national joint registries studies and randomised controlled trials.

Are Orthopaedic Clinical Trials Linguistically and Culturally Diverse? A Systematic Review

Purpose

Underrepresentation and misrepresentation of historically underrepresented populations in randomized controlled trials (RCTs) may have implications for the validity of research results and their application for diverse populations. To evaluate the representation of historically linguistically, racially, and ethnically underrepresented participants in orthopaedic randomized controlled trials (RCTs) and to assess the use of translated and culturally adapted patient reported outcome measures (PROMs).

Methods

Separate and comprehensive literature searches of PubMed, Web of Science, and Embase databases were performed to identify RCTs utilizing PROMs between the years 2012 - 2022 among the top five highest 5-year impact factor orthopaedic journals according to the 2021 Journal Citation Reports database. The primary outcomes of interest included reporting of linguistic, racial and ethnic demographic characteristics of trial participants and the utilization of translated PROMs. The methodological quality of each clinical trial was assessed using the Jadad Criteria.

Results

230 RCTs met inclusion criteria. The language of participants was reported in 14% of trials and in 17% of trials when searching both the published text and clinical trial registration information. In addition, race and/or ethnicity was reported in 11% of trials, and the use of translated PROMs was reported in 7% of trials. Among the six multinational studies, none reported the language of the study population nor the use of translated PROMs. Notably, four studies (2%) reported utilizing culturally adapted PROMs. The average Jadad score was 3.07.

Conclusion

Participant language, race, and ethnicity are infrequently reported in orthopaedic clinical trials, potentially limiting the application and interpretation of study results. Similarly, the linguistic and cultural adaptation of PROMs utilized are often not reported, which also limits interpretations of the validity and generalizability of orthopedic study results. Researchers and journals should promote standard reporting of demographic data and methods of PROM adaptation to ensure results are generalizable to diverse patient populations.

Level of Evidence

III.

Stemmed Tibial Fixation for Primary Total Knee Arthroplasty in Obese Patients-A National Registry Study

BACKGROUND

We investigated if the use of augmented tibial fixation with stems in primary total knee arthroplasty (TKA) in obese patients was associated with a difference in reason for revision, type of revision, or overall revision rate.

METHODS

Data from the Australian Orthopaedic Association National Joint Replacement Registry compared reason for revision, rate, and type of revision between primary TKA using stemmed tibial prostheses to nonstemmed prostheses, stratified by body mass index (BMI) and obesity. The cumulative percent revision was obtained using the Kaplan-Meier method, and Cox proportional hazards models estimated hazard ratios (HRs) adjusted for age and sex with 95% confidence intervals (CIs). All tests were 2-tailed at 5% statistical significance (P < .05). There were 66,508 procedures available for analyses.

RESULTS

Obese class 2 (BMI 35 to 39.99) had higher rates of revision in the stemmed group compared to the nonstemmed group (HR 1.44, 95% CI 1.00, 2.05, P = .047). There was no significant difference in revision rates between stemmed and nonstemmed tibial prostheses in any other BMI group. Primary TKA in obese patients (BMI ≥30) with a stem extension had a significantly higher rate of minor revisions compared to no stem extension (HR 1.31, 95% CI 1.03, 1.66, P = .025). There was no significant difference between stemmed and nonstemmed groups for major revision in obese patients and for minor or major revision in nonobese patients.

CONCLUSION

Using a tibial stem during primary TKA in obese patients is not associated with a lower rate of revision.

Go Big or Go Home: Obesity and Total Joint Arthroplasty

Obesity is highly prevalent, and it is expected to grow considerably in the United States. The association between obesity and an increased risk of complications following total joint arthroplasty (TJA) is widely accepted. Many believe that patients with body mass index (BMI) >40 have complications rates that may outweigh the benefits of surgery and should consider delaying it. However, the current literature on obesity and outcomes following TJA is observational, very heterogeneous, and full of confounding variables. BMI in isolation has several flaws and recent literature suggests shifting from an exclusively BMI <40 cutoff to considering 5 to 10% preoperative weight loss. BMI cutoffs to TJA may also restrict access to care to our most vulnerable, marginalized populations. Moreover, only roughly 20% of patients instructed to lose weight for surgery are successful and the practice of demanding mandatory weight loss needs to be reconsidered until convincing evidence exists that supports risk reduction as a result of preoperative weight loss. Obese patients can benefit greatly from this life-changing procedure. When addressing the potential difficulties and by optimizing preoperative assessment and intraoperative management, the surgery can be conducted safely. A multidisciplinary patient-centered approach with patient engagement, shared decision-making, and informed consent is recommended.

Stemmed Versus Nonstemmed Tibia in Primary Total Knee Arthroplasty: A Similar Pattern of Aseptic Tibial Loosening in Obese Patients with Moderate Varus. 5-Year Outcomes of a Randomized Controlled Trial

Obesity is linked to early tibial tray failure after primary total knee arthroplasty (TKA) for osteoarthritis (OA), especially in patients with preoperative varus. This study compared standard and stemmed tibiae TKAs in patients with class I and II obesity with varus deformity. Between April 2013 and June 2020, a prospective study was conducted including patients with end-stage OA, body mass index between 30 and 40 kg/m2, and varus <15 degrees. Patients were randomly assigned to TKAs with either standard or long-stemmed tibiae and evaluated 5 years after surgery using the Knee Society Scoring (KSS). The knee society and modified radiographic evaluation systems were used for radiological evaluation. In total, 264 TKAs were performed in 264 patients (134 in the standard group and 130 in the stemmed group). The mean preoperative hip-knee-ankle angles for the standard and stemmed groups were 8.2 ± 3.2 degrees/varus and 9 ± 2.9 degrees/varus, respectively (p = 0.2), which improved to 5.1 ± 3 degrees/valgus and 5 ± 3.5 degrees/valgus after surgery (p = 0.52). There was no statistically significant difference between the objective KSS (92 vs. 92.9; p = 0.84) and the functioning KSS (73.4 vs. 74.8; p = 0.28). There were no aseptic loosening cases or radiographic differences. In-group analysis revealed significant outcomes differences in both groups if preoperative varus was >10 degrees irrespective of the stem design (p < 0.0001). Complications occurred in two patients; one with a late infection and one had a stem-related tibial fracture. Standard tibia TKAs yielded comparable results in obese patients to long-stemmed tibias. No aseptic tibial loosening was observed regardless of stem type, and worse clinical outcomes were associated with greater varus. CLINICAL TRIAL REGISTRY::  registered at http://www.researchregistry.com (researchregistry5717).LEVEL OF EVIDENCE: II; a prospective randomized trial.

Total knee arthroplasty in patients with severe obesity: outcomes of standard keeled tibial components versus stemmed universal base plates

BACKGROUND

Patients with severe obesity [body mass index (BMI) ≥ 40 kg/m²] potentially overload the tibial component after total knee arthroplasty (TKA), risking tibial subsidence. Using a cemented single-radius cruciate-retaining TKA design, this study compared the outcomes of two tibial baseplate geometries in patients with BMI ≥ 40 kg/m²: standard keeled (SK) or universal base plate (UBP), which incorporates a stem.

METHODS

This was a retrospective, single-centre cohort study with minimum 2 years follow-up of 111 TKA patients with BMI ≥ 40 kg/m²: mean age 62.2 ± 8.0 (44-87) years, mean BMI 44.3 ± 4.6 (40-65.7) kg/m² and 82 (73.9%) females. Perioperative complications, reoperations, alignment and patient-reported outcomes (PROMS): EQ-5D, Oxford Knee Score (OKS), Visual Analogue Scale (VAS) pain score and satisfaction were collected preoperatively, and at 1 year and final follow-up postoperatively.

RESULTS

Mean follow-up was 4.9 years. SK tibial baseplates were performed in 57 and UBP in 54. There were no significant differences in baseline patient characteristics, post-operative alignment, post-operative PROMs, reoperations or revisions between the groups. Three early failures requiring revision occurred: two septic failures in the UBP group and one early tibial loosening in the SK group. Five-year Kaplan-Meier survival for the endpoint mechanical tibial failure was SK 98.1 [94.4-100 95% confidence interval (CI)] and UBP 100% (p = 0.391). Overall varus alignment of the limb (p = 0.005) or the tibial component (p = 0.031) was significantly associated with revision and return to theatre.

CONCLUSIONS

At early to mid-term follow-up, no significant differences in outcomes were found between standard and UBP tibial components in patients with BMI ≥ 40 kg/m². Varus alignment of either tibial component or the limb was associated with revision and return to theatre.

Could Novel Radiographic Findings Help Identify Aseptic Tibial Loosening?

BACKGROUND

Aseptic loosening following total knee arthroplasty remains one of the leading causes of long-term failure. Radiographic identification of loose implants can be challenging with standard views. The purpose of this study was to compare the incidence of novel radiographic findings of anterior heterotopic bone formation and medial or lateral cyst formation in patients who have aseptic loosening to patients who have well-fixed implants.

METHODS

A retrospective radiographic review was performed on 48 patients' revised secondary to aseptic tibial loosening. This cohort was compared to two additional cohorts; 48 patients returning for routine postoperative follow-up (control 1), and 48 patients revised secondary to infection or instability who had well-fixed implants (control 2).

RESULTS

There were 41 of 48 (85%) patients who had implant loosening and were noted to have anterior heterotopic bone formation compared to 1 of 48 (2%) patients in control 1 and 3 of 48 (6%) patients in control 2 (P ≤ .0001). There were 43 of 48 (90%) patients who had implant loosening and had medial cyst formation compared to 3 of 48 (6%) patients in control 1 and 5 of 48 (10%) in control 2 (P ≤ .0001). There were 42 of 48 (88%) patients who had implant loosening and had lateral cyst formation compared to 2 of 48 (4%) patients in control 1 and 4 of 48 (8%) in control 2 (P ≤ .0001).

CONCLUSION

In this study, we describe novel radiographic findings of anterior heterotopic bone formation and cysts that develop in patients who have aseptic loosening following primary total knee arthroplasty. We believe that these radiographic features may lead to easier identification of aseptic loosening.

Total Knee Arthroplasty with Non-Stemmed Tibial Components among Obese Patients: Clinical and Radiologic Evaluation and Review of Literature

Objective

This study aimed to evaluate the radiologic and clinical outcomes of TKA with non-stemmed tibial components in relation to their body mass index (BMI).

Methods

In this retrospective cohort study, the outcome of TKA with non-stemmed tibial components based on their BMI was evaluated (BMI<30 vs. BMI≥30). The patients' function was assessed using the International Knee Documentation Committee (IKDC) and Lysholm knee questionnaires. Radiologic evaluation for probable signs of loosening was performed using two quantitative scoring systems by Ewald and Bach et al. Moreover, we reviewed the current literature on the application of non-stemmed tibial components in obese patients.

Results

Twenty-one patients (two men and 19 women) with BMI≥30 and a mean age of 65.1±9.5 years, and 22 patients (three men and 19 women) with BMI<30 and a mean age of 63.6±8.5 years were studied. The mean follow-up periods with BMI≥30 (47.0±19.8 months) and BMI<30 (49.2±18.7 months) were comparable (p=0.618). No patients in either group experienced clinical loosening. Besides, none of the patients had any kind of revision surgery. The patients in both BMI groups had comparable IKDC scores (both the total score and its sub-scores; p>0.05). Furthermore, the total Lysholm knee scores were similar in both groups (p=0.122). Using both scoring systems, the peri-prosthetic bone radiolucency near the tibial components was similar in both groups (p>0.999).

Conclusion

The present study found no significant difference in the radiologic or clinical outcome of non-stemmed TKA in patients with BMIs under and over 30.

High Survivorship of a Modular Titanium Baseplate Independent of Body Mass Index and Malalignment

BACKGROUND

Tibial component aseptic loosening remains problematic in primary total knee arthroplasty (TKA). Influential factors include component design, metallurgy, and cement technique. Additionally, reports advocate for longer tibial stem fixation in high body mass index (BMI) patients. We have utilized a single stem length modular titanium baseplate in patients regardless of BMI, bone quality, or malalignment. We report the survivorship of this implant with focus on the impact of elevated BMI and postoperative malalignment.

METHODS

We retrospectively reviewed patients who underwent TKA with a single modular titanium baseplate with a cruciate-shaped keel between 2004 and 2018. In total, 2,949 TKAs with a minimum of 1-year follow-up were included. The mean follow-up was 7 years. The primary outcome was component failure stratified by BMI and postoperative malalignment. High viscosity cement was utilized in all cases. Chi-squared and t-tests were used to compare outcome variables across groups.

RESULTS

Eighty-five implants (2.8%) were revised with 46 (1.6%) for aseptic loosening. Failure was not associated with BMI, gender, American Society of Anesthesiologists class, or Charlson Comorbidity Index. There was no difference in failure rate by BMI (P = .26) or by malalignment (outside of 3° from neutral mechanical axis) (P = .67). Age was associated with failure as patients with failed TKAs were younger (61 vs 65, P < .01).

CONCLUSION

This design of a specific modular titanium base plate with a cruciate-shaped keel and grit blast surface demonstrated 99% survivorship regardless of patient BMI or malalignment over 7-year follow-up period. Consistent cement technique with high viscosity cement indicates that component design remains an important variable impacting survivorship in TKA.

Slight femoral under-correction versus neutral alignment in total knee arthroplasty with preoperative varus knees: a comparative study

Background

This study aimed to compare the short-term clinical results of slight femoral under-correction with neutral alignment in patients with preoperative varus knees who underwent total knee arthroplasty.

Methods

The medical records and imaging data were retrospectively collected from patients who had undergone total knee arthroplasty in our hospital from January 2016 to June 2019. All patients had varus knees preoperatively. Upon 1:1 propensity score matching, 256 patients (256 knees) were chosen and divided into a neutral alignment group (n=128) and an under-correction group (n=128). The patients in the neutral group were treated with the neutral alignment. In the under-correction group, the femoral mechanical axis had a 2° under-correction. The operative time, tourniquet time and the length of hospital stay in the two groups were recorded. The postoperative hip-knee-ankle angle, frontal femoral component angle and frontal tibial component angle were measured. Patient-reported outcome measures were also compared.

Results

The operative time, tourniquet time and the length of hospital stay in the under-correction group were significantly shorter than the neutral alignment group (P<0.05). At the 2-year follow-up, the under-correction group had a larger varus alignment (P<0.05) and a larger frontal femoral component angle (P<0.05), and the frontal tibial component angles of the two groups were comparable. Compared with the neutral alignment group, the slight femoral under-correction group had significantly better patient-reported outcome measures scores (P<0.05).

Conclusion

For varus knees treated with total knee arthroplasty, alignment with a slight femoral under-correction has advantages over the neutral alignment in terms of the shorter operative time and better short-term clinical results.

Level of evidence

III

Varus Collapse in Total Knee Arthroplasty: Does Fixation or Bone Fail First?

INTRODUCTION

Aseptic tibial loosening is now considered the most common reason that total knee arthroplasties (TKA) fail long term. There are unique subsets of patients that fail into varus alignment of the tibial tray with collapse of the medial proximal tibia. It is currently unknown if the implant fixation fails first or if the proximal medial tibia collapses first.

MATERIALS

We performed a retrospective analysis of 88 patients that were revised at our institution secondary to aseptic varus collapse of the proximal tibia. Two fellowship-trained arthroplasty surgeons performed a retrospective analysis on sequential precollapse radiographs in each patient to determine which failed first: the implant fixation (implant-cement or cement-bone interface) or the medial proximal tibia.

DISCUSSION

36/88 (40.9%) patients had a series of precollapse radiographs that could be reviewed. Failure at the implant-cement interface before varus collapse in 23 vs 22 patients, failure at the implant-cement and cement-bone interface before varus collapse in two patients, and contemporaneous failure at the implant-cement interface and varus collapse in 11 vs 12 patients were identified by reviewers one and two, respectively.

CONCLUSION

The most frequent mechanism of failure identified was failure of the implant-cement interface followed by subsequent medial tibial varus collapse. Improving implant fixation may decrease the incidence of this unique failure mechanism. We advocate the use of supplemental stem fixation in high-risk patients and optimal cement techniques for all patients as methods of potentially avoiding tibial varus collapse, one of the most frequent modes of long-term failure.

Tibial Tray with a Stem: Does It Have Any Role in Primary Cemented Total Knee Replacement?

Over many decades, total knee replacement (TKR) has become the ideal treatment option for advanced arthritis. Many designs were introduced to increase the stability of the tibial tray, hence the longevity of the prosthesis. This retrospective study was performed on 168 patients who received NexGen cemented primary total knee either with standard tibial tray (group A) or tibial tray with an intramedullary stem (group B) between May 2008 and May 2017. We reviewed all preoperative and postoperative clinical and radiological data retrospectively. In addition, a prospective clinical and radiological reassessment was done. Our aim was to answer the following questions: (1) Is there any difference between both groups in regard to clinical and radiological results? (2) Is there any difference in the revision rate? (3) Is there a role of using stemmed tibial tray in primary TKR? Better results were recorded in obese and severely obese patients having stemmed cemented tibial tray and so for patients with marked and severe preoperative varus angle. Our recommendations are to use cemented tibial tray with a stem in complicated primary surgery without fear of adverse effects on short and intermediate terms of follow-up.

Where Is the "Weak Link" of Fixation in Contemporary Cemented Total Knee Replacements?

BACKGROUND

Aseptic tibial loosening is a frequent cause of long-term failure following primary cemented total knee replacement. Failure of the tibial implant can occur at the implant-cement interface or at the cement-bone interface. Currently, it is unknown at which interface failure occurs in cases of aseptic tibial loosening. The following study was designed to determine which interface represents the "weak link" for tibial implant fixation.

METHODS

We performed a retrospective analysis of 149 patients who were revised secondary to aseptic tibial loosening at our institution from 2005 to 2017. Operative reports and radiographs were reviewed on each patient to determine the location and pattern of fixation failure.

RESULTS

Implant failure was more prevalent at the implant-cement than cement-bone interface, 140/149 (94.0%) vs 9/149 (6.0%). Additionally, we noted 2 distinct patterns of failure in patients that loosened at the implant-cement interface. Ninety of 140 (64.3%) patients developed varus collapse pattern of failure. Forty-nine of 140 (35.0%) patients developed failure between the implant-cement interface without angulation. All 149 patients had heterotopic bone formation anterior to the tibial baseplate, which was consistent regardless of which interface failed.

CONCLUSION

The most frequent interface failure identified in our study was at the implant-cement interface, 140/149 (94.0%). This finding has substantial clinical ramifications. Because failure was predominantly at the implant-cement interface there may be design opportunities for increasing implant fixation to cement. Implants with improved undersurface tibial tray features may be necessary to mitigate the risk of failure at this interface, especially in overly active patients or those with elevated body mass indices.

A Prophylactic Tibial Stem Reduces Rates of Early Aseptic Loosening in Patients with Severe Preoperative Varus Deformity in Primary Total Knee Arthroplasty

BACKGROUND

Patients with a preoperative varus deformity >8 degrees are at increased risk of aseptic loosening after total knee arthroplasty. This study analyzes the effect of a tibial stem on the rate of aseptic loosening in patients with a severe preoperative varus deformity.

METHODS

Patients with a preoperative varus deformity of >8 degrees and 2-year minimum follow-up with a stemmed tibial component (n = 67) were matched 1:2 to patients with a similar preoperative varus deformity with a standard tibial component (n = 134). Radiolucent lines were measured on the tibia at 6 weeks, 1 year, and 2 years postoperatively using the Knee Society Radiographic Evaluation System. Failure was defined as revision due to aseptic loosening of the tibial component. Outcomes were evaluated using Student's t-tests and log-rank tests.

RESULTS

Patients with tibial stems had greater preoperative deformity (12.9 vs 11.3 degrees, P = .004). There was no difference in postoperative alignment (1.7 vs 2.1 degrees varus, P = .25) or tibial component angle (1.8 vs 2.1 degrees varus, P = .33). Patients with stems were more likely to have more constraint (44.8% vs 1.5%, P < .001). Progression of radiolucent lines >2 mm was observed in 17.6% (23/134) vs 5.97% (4/67) of patients in the stem group (P = .03). Rates of aseptic loosening were lower in the stem group (0% vs 5.15%, P = .05).

CONCLUSION

Despite worse preoperative deformity and higher utilization of constraint, tibial stem use in patients with severe preoperative varus deformity resulted in lower rates of aseptic loosening. Prophylactic use of stems in these patients may help increase implant survival.

Modular Tibial Stem Use and Risk of Revision for Aseptic Loosening in Cemented Primary Total Knee Arthroplasty

BACKGROUND

Modular tibial stem extensions in total knee arthroplasty (TKA) are designed to reduce the risk of aseptic loosening of the tibial base plate. However, these implants add significant cost and an evaluation of their effectiveness in reducing this risk of loosening has not been studied in a large cohort. We sought to evaluate modular tibial stem utilization in primary TKA.

METHODS

We conducted a cohort study using our integrated healthcare system's Total Joint Replacement Registry. Patients who underwent cemented primary TKA were identified (2009-2019). Propensity scores were used to 1:1 match patients without to those with a stem extension. Cox proportional-hazards regression was used to evaluate the risk for revision due to aseptic loosening.

RESULTS

Ten thousand four hundred seventy six TKA with a modular tibial stem were matched to 10,476 TKA without a tibial stem. Stem utilization associated with a lower risk of revision for loosening across all postoperative follow-up (hazard ratio = 0.38, 95% confidence interval = 0.17-0.85).

CONCLUSION

In a matched cohort study, we observed presence of a stem extension was associated with a lower risk of revision for aseptic loosening. Further study to identify specific risk factors for aseptic loosening and confirm the findings presented here are warranted.

LEVEL OF EVIDENCE

Level III.

Increased survival rate in extension stemmed TKA in obese patients at minimum 2 years follow-up

PURPOSE

Total knee arthroplasty (TKA) is frequently performed for obese patients. TKA in this population shows a high rate of complication, particularly tibial component loosening. The aim of this study is to compare the survival rate of tibial components in obese population using TKA with stem versus without stem.

METHODS

From a prospective database of 4216 TKA, obese patients [body mass index (BMI) > 30 kg m²] with primary TKA using a tibial short stem extension (30 mm) at a minimum follow-up of 2 years were retrospectively reviewed and compared to a matched control group (1:3 ratio) with a standard tibial stem. Inclusion criteria were BMI > 30 kg m², first knee surgery and 24 months minimum of follow-up. The primary outcome was revision for tibial aseptic loosening. Secondary outcomes were all-cause revisions and Knee Society Scores (KSS).

RESULTS

The final study population consisted of 35 TKA with tibial extension stem versus 105 TKA with standard stem. The mean age was 69.2 and 69.5 years, respectively, with a mean follow-up of 52 months. Both groups were comparable before surgery. After 2 years of follow-up, we observed seven tibial loosening in the group without stem (6.6%) versus no tibial loosening in the stemmed group (p < 0.001). The difference in KSS knee score (83 versus 86; p = 0.06) and the KSS function score (73 versus 77; p = 0.84) were not statistically significant at the final follow-up.

CONCLUSION

Using stemmed TKA for obese patients significantly decreased tibial loosening rate at minimum 2 years of follow-up.

LEVEL OF EVIDENCE

Case-control study, Level III.

A comparative prospective study between stemmed versus an unstemmed tibial component in total knee arthroplasty in obese patients

BACKGROUND

There is no consensus in the literature regarding the patients with obesity who do well with TKA, or this group is at risk of a variety of complications. Implant choices between the two types of implants which either long or standard stem can improve the likelihood that a patient with obesity will achieve high scores for function and quality of life after TKA.

METHODS

This prospective clinical study included 200 patients who were categorized into two groups: group (1) traditional (standard) unstemmed cemented tibial tray (n = 100 patients) and group (2) stemmed cemented tibial tray with the cementless press-fit stem (n = 100 patients).

RESULTS

The average follow-up was (7.6 ± 1 years) (range from 6.5 up to 10 years). The average age of the stemmed group was 55.69 ± 8.45 and for the unstemmed group was 57.3 ± 7.8. The average BMI for the stemmed patients was 38.84 ± 3.89, while for the standard (unstemmed) group was 40.0 ± 3.95. Functional results showed significant improvement in both groups but more in the stemmed group (LS) as the difference and change between pre and post were more significant at long stem (P > 0.001).

CONCLUSION

Based on our results, there were significant improvements in both groups either stemmed or unstemmed TKA but more in the stemmed group which had higher functional outcomes compared to the unstemmed group.

LEVEL OF EVIDENCE

IV.

Revision Rates and Functional Outcomes Among Severely, Morbidly, and Super-Obese Patients Following Primary Total Knee Arthroplasty: A Systematic Review and Meta-Analysis

BACKGROUND

Obesity has been associated with a greater burden of symptomatic knee osteoarthritis. There is some evidence that patients with a very high body mass index (BMI) may have a higher risk of complications and poor outcomes following total knee replacement compared with non-obese patients or obese patients with a lower BMI. We hypothesized that increasing degrees of obesity would be associated with deteriorating outcomes for patients following total knee replacement.

METHODS

We performed a comprehensive systematic review of 4 medical databases (MEDLINE, AMED, Ovid Healthstar, and Embase) from inception to August 2016. We extracted data to determine revision risk (all-cause, septic, and aseptic) and functional outcome scores (Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC], Knee Society Score, Oxford Knee Score, EuroQol-5D, and Short Form [SF]-12 Physical Component Summary) in patients with severe obesity (BMI ≥35 kg/m), morbid obesity (BMI ≥40 kg/m), and super-obesity (BMI ≥50 kg/m) in comparison with patients with a normal BMI (<25 kg/m). Meta-analysis was performed using a random effects model.

RESULTS

We screened 3,142 titles and abstracts and 454 full-text articles to identify 40 eligible studies, of which 37 were included in the meta-analysis. Compared with patients with a normal BMI, the risk ratio for an all-cause revision surgical procedure was 1.19 (95% confidence interval [CI], 1.03 to 1.37; p = 0.02) in patients with severe obesity, 1.93 (95% CI, 1.27 to 2.95; p < 0.001) in patients with morbid obesity, and 4.75 (95% CI, 2.12 to 10.66; p < 0.001) in patients with super-obesity. The risk ratio for septic revision was 1.49 (95% CI, 1.28 to 1.72; p < 0.001) in patients with severe obesity, 3.69 (95% CI, 1.90 to 7.17; p < 0.001) in patients with morbid obesity, and 4.58 (95% CI, 1.11 to 18.91; p = 0.04) in patients with super-obesity. There were no significant differences (p > 0.05) in risk of aseptic revision. Based on the Knee Society Scores reported in a single study, patients with super-obesity had outcome scores, expressed as the standardized mean difference, that were 0.52 lower (95% CI, 0.80 lower to 0.24 lower; p < 0.001) than non-obese controls; however, no difference was observed for severe or morbidly obese patients.

CONCLUSIONS

The risk of septic revision is greater in patients with severe obesity, morbid obesity, and super-obesity, with progressively higher BMI categories associated with a higher risk. However, the risk of aseptic revision was similar between all obese and non-obese patients. Functional outcome improvements are also similar, except for super-obese patients, in whom data from a single study suggested slightly lower scores. These findings may serve to better inform evidence-based clinical, research, and policy decision-making.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Metaphyseal Stem Extension Improves Tibial Stability in Cementless Total Knee Arthroplasty

BACKGROUND

The goal was to determine if the addition of a metaphyseal stem extension limits micromotion of a cementless tibial component during cyclic loading in primary total knee arthroplasty. The hypothesis tested was that the use of a 50-mm stem extension on a cementless tibial component would limit motion compared with an identical cementless component without a stem extension.

METHODS

The study used 3 variations of a tibial component from the same total knee arthroplasty system. Group 1 consisted of a cementless tibial component without a stem extension. Group 2 used the same cementless component as group 1, but with the addition of a short 50-mm stem. Group 3 consisted of a cemented tibial component without a stem extension to serve as a "control" (gold standard). The tibial specimens were implanted into a synthetic bone model and tested using a physiological medial-lateral 60/40 load distribution for 5000 cycles.

RESULTS

The results demonstrated a significant decrease in motion at the anterior region of the cementless stem extension (group 2) components compared with the cementless with no stem extension (group 1). The cementless with stem extension (group 2) demonstrated similar results at all cycles to the cemented (group 3) components at the anterior region.

CONCLUSION

The addition of a short metaphyseal stem (50mm) to a keel plus 4-peg tibial component design provides a significant reduction in micromotion during cyclic loading of a cementless tibial baseplate in a synthetic foam bone model, similar to a cemented implant.

Pathogenesis and clinical management of obesity-related knee osteoarthritis: Impact of mechanical loading

Obesity-related osteoarthritis (OA) is a complex, multifactorial condition that can cause significant impact on patients' quality of life. Whilst chronic inflammation, adipocytokines and metabolic factors are considered to be important pathogenic factors in obesity related OA, there has been limited investigation into the biomechanical impact of obesity on OA development. This review aims to demonstrate that mechanical factors are the major pathological cause of obesity-related OA. The effect of obesity on pathological changes to the osteochondral unit and surrounding connective tissues in OA is summarized, as well as the impact of obesity-related excessive and abnormal joint loading, concomitant joint malalignment and muscle weakness. An integrated therapeutic strategy based on this multi-factorial presentation is presented, to assist in the management of obesity related OA.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

Despite the high prevalence of obesity-related OA, there is no specific guideline available for obesity-related OA management. In this review, we demonstrated the pathological changes of obesity-related OA and summarized the impact of biomechanical factors by proposing a hypothetical model of obesity-related OA change. Therapeutic strategies based on adjusting abnormal mechanical effects are presented to assist in the management of obesity-related OA.

Reduced Aseptic Loosening With Fully Cemented Short-Stemmed Tibial Components in Primary Cemented Total Knee Arthroplasty

BACKGROUND

Recently, the use of short tibial stems in the obese population undergoing total knee arthroplasty (TKA) has been proposed. Thus, we designed a study to assess tibial component survivorship after primary TKA using a single implant both with and without a fully cemented stem extension performed by a single surgeon.

METHODS

A search of our institutional research database was performed. A minimum 2-year follow-up was selected. Cohorts were created according to patient body mass index (BMI; >40 kg/m² and <40 kg/m²) and the presence (stemmed tibia [ST]) or absence (non-stemmed tibia [NST]) of a short tibial stem extension. Kaplan-Meier survival analyses for aseptic loosening and log-rank tests were performed.

RESULTS

A total of 236 patients were identified (ST = 162, NST = 74). Baseline patient characteristics were statistically similar between cohorts with the exception of BMI which was greater in the ST cohort (32.9 kg/m², 30.6 kg/m²; P = .01). Kaplan-Meier survival analysis at 5 years was superior for the BMI < 40 kg/m² cohort (98.9%, 93.1%; P = .045), the ST cohort (100%, 94.5%; P = .006), and the BMI > 40 kg/m² with ST cohort at 4 years (71.4%, 100%; P = .008).

CONCLUSION

Morbid obesity and a short native tibial stem design appear to be associated with aseptic loosening in primary TKA. This appears to be mitigated through the use of an ST. As such, the use of ST may be considered in at-risk patients. Alternatively, implants with longer native stem designs can be employed. Modern short-stemmed tibial components may need to be redesigned.

Lower limb joint repair and replacement: an overview

In the last few years, much has been published concerning total joint arthroplasty, and debates and discussions to new questions and points of view started many years ago. In this commentary, we report the latest evidence of best practice in the field of lower limb arthroplasty; this evidence is based on a literature search conducted by using PubMed and Scopus databases with a time limit of five years. We found novel evidence regarding cemented and not cemented implant, implant design, anticoagulant use, tourniquets, and other aspects of joints replacement surgery that we consider a common part of modern orthopedic practice. We specifically focus on lower limb joint replacement.

The minimum clinically important difference for the Japanese version of the new Knee Society Score (2011KSS) after total knee arthroplasty

BACKGROUND

The new Knee Society Score (2011KSS) has been used to evaluate post-operative outcomes after total knee arthroplasty (TKA). However, there is no minimum clinically important difference (MCID) for 2011KSS. The purpose of this study is to define MCID of 2011KSS after TKA.

METHODS

Patients who underwent primary TKA for primary knee osteoarthritis between April 2012 and December 2016 were included in the study. The Japanese version of 2011KSS and original Knee Society Score (OKSS) were recorded preoperatively and at one-year postoperatively. With improvement in pain score of OKSS as an anchor, an anchor-based approach was used to identify the MCID of 2011KSS. The improvement in pain of OKSS was classified into 5 categories. The MCID was determined using a linear regression analysis of delta 2011KSS against improvement in the category of pain in OKSS. The MCID for 2011KSS expectation was not calculated because the items of pre- and post-operative questionnaires were different.

RESULTS

Five hundred and twenty-two cases were enrolled (age: 74.8 ± 7.3 years, female: 80.0%). After 1-year follow-up, 344 TKAs were finally included (age: 74.6 ± 7.1 years, female: 77.9%). Linear regression analyses showed that MCID for 2011KSS was 1.9 (95% confidential interval (CI): 1.3-2.5) in symptom, 2.2 (95%CI: 1.4-2.9) in satisfaction, and 4.1 (95%CI: 2.5-5.7) in functional activities.

CONCLUSIONS

MCID for 2011KSS was successfully calculated. These MCID values make the 2011KSS a more efficient tool for evaluating the physical activities of the populations of patients undergoing TKA. These MCID values can also be used to calculate sample size to evaluate the power of a study in designing clinical studies.

Prophylactic Tibial Stem Fixation in the Obese: Comparative Early Results in Primary Total Knee Arthroplasty

Purpose

Obesity is a risk factor for aseptic loosening after total knee arthroplasty (TKA). Prophylactic use of tibial stems may enhance tibial fixation in obese patients. The aim of this study was to determine whether a tibial stem extension decreases rates of early failure in obese patients.

Materials and Methods

This study included 178 consecutive primary TKAs (143 patients) with a body mass index ≥35 kg/m². Fifty TKAs were performed with the use of a 30 mm tibial stem extension, and 128 TKAs were performed with a standard tibial component. Patients with two-year clinical follow-up were included. The primary outcome was revision for aseptic loosening. Secondary outcomes were all-cause revision and radiolucent lines (RLLs) on radiographs.

Results

Average follow-up was 34 months (range, 24 to 46 months). No failures for aseptic loosening occurred. The occurrence of secondary procedures was not significantly different between groups. Quantification of RLLs revealed no difference between groups.

Conclusions

At early follow-up, no difference was measured in revision rates, need for subsequent procedures, or RLLs between groups.

Failure After Modern Total Knee Arthroplasty: A Prospective Study of 18,065 Knees

BACKGROUND

We sought is to determine the mechanism of failure among primary total knee arthroplasties (TKAs) performed at a single high-volume institution by asking the following research questions: (1) What are the most common failure modes for modern TKA designs? and (2) What are the preoperative risk factors for failure following primary TKA?

METHODS

From May 2007 to December 2012, 18,065 primary TKAs performed on 16,083 patients at a single institution were recorded in a prospective total joint arthroplasty registry with a minimum of 5-year follow-up. We retrospectively reviewed patient charts to determine a cause of failure for primary TKAs. A cox proportional hazard model was used to determine the risk of revision surgery following primary TKA.

RESULTS

The most common reasons for failure within 2 years after TKA were infection and stiffness. The multivariable regression identified the following preoperative risk factors for TKA failure: history of drug abuse (hazard ratio [HR] 4.68; P = 0.03), deformity/mechanical preoperative diagnosis (HR 3.52; P < .01), having a constrained condylar knee implant over posterior-stabilized implant (HR 1.99; P < .01), post-traumatic/trauma preoperative diagnosis (HR 1.78; P = .03), and younger age (HR 0.61; P < .01) CONCLUSION: These findings add to the growing data that primary TKAs are no longer failing from polyethylene wear-related issues. This study identified preoperative risk factors for failure of primary TKAs, which may be useful information for developing strategies to improve outcomes following TKA.

Reconstruction of Disrupted Extensor Mechanism After Total Knee Arthroplasty

BACKGROUND

Disruption of the extensor mechanism after total knee arthroplasty (TKA) is a debilitating complication that results in extension lag, limited range of motion, difficulty in walking, frequent falls, and chronic pain. This study presents the clinical and radiographic results of reconstruction after extensor mechanism disruption in TKA patients.

METHODS

Consecutive patients with allograft reconstruction of extensor mechanism after TKA were identified retrospectively from an academic tertiary center for revision TKA.

RESULTS

Sixteen patients with a mean age of 61 ± 14 years at extensor mechanism reconstruction with a minimum of 2-year follow-up were included. The mean follow-up was 3.3 ± 2.2 years. Knee Society score (KSS), before and at final follow-up extension lag, range of motion, and radiographic change in patellar height were reviewed. There were statistically significant improvements between preoperative and final follow-up KSS (P < .001; KSS for pain, preoperative 40 ± 14 points to final follow-up 67 ± 15 points [P < .001]; KSS for function, preoperative 26 ± 21 points to final follow-up 48 ± 25 points [P < .001]). The extension lag was also reduced from 35° ± 16° preoperatively to 14° ± 18° (P < .001) at final follow-up. There was an average proximal patellar migration of 8 ± 10 mm. Five (31%) cases had an extensor lag of >30° or revision surgery for repeat extensor mechanism reconstruction, infection, or arthrodesis.

CONCLUSION

Our 10-year experience using allografts during extensor mechanism reconstruction demonstrates reasonable outcomes, but failures are to be anticipated in approximately one-third of patients.

Initial stability of a new cementless fixation method of a tibial component with polyaxial locking screws: a biomechanical in vitro examination

INTRODUCTION

Cementless fixation of the tibial component is critical as reduced initial stability leads to implant failure. In this experimental in vitro study, a new fixation method of the tibial component using polyaxial locking screws is evaluated using Roentgen stereophotogrammetric analysis (RSA).

MATERIALS AND METHODS

A special prototype of a tibial component with four polyaxial locking screws was tested on 10 fresh-frozen human tibia specimens. The components were tested with an axial load of 2000 N for 10,000 cycles. Radiographs in two views were performed before loading, after 1000 and after 10,000 cycles, respectively. Besides rotation and translation along the x-, y-, and z-axes, endpoints for RSA were maximum subsidence (MaxSub), maximum lift off (MaxLiftOff) and maximum total point motion (MTPM).

RESULTS

MaxSub increased from -0.5 mm (SD = 0.2) after 1000 cycles to -0.9 mm (SD = 1.1). MaxLiftOff was 0.1 mm after 1000 cycles and did not increase after 10,000 cycles. The MTPM was 0.7 mm (SD = 0.3) after 1000 cycles and 1.1 mm (SD = 1.1) after 10,000 cycles. Two out of nine implants showed an MTPM ≥ 1.0 mm after 10,000 cycles.

CONCLUSIONS

Polyaxial locking screws can potentially improve the initial stability of tibial components. The results of this study indicate that the use of such screws in total knee arthroplasty may be of interest in the future. Further experimental and clinical investigation is needed.