A Current Prosthesis With a 1-mm Thickness Increment for Polyethylene Insert Could Result in Fewer Adjustments of Posterior Tibial Slope in Cruciate-Retaining Total Knee Arthroplasty

Frequent complications of deficient patellae after component removal in 1.5-stage exchange arthroplasty for periprosthetic joint infection

PURPOSE

To compare the complication rates between deficient patellae (remnant patellae after component removal) and non-resurfaced patellae after 1.5-stage exchange arthroplasty for periprosthetic joint infection and identify risk factors for complications of deficient patellae.

METHODS

Complications in 76 deficient patellae (group D) and 41 non-resurfaced patellae (group N), with a minimum follow-up of 2 years after 1.5-stage exchange arthroplasty were retrospectively analyzed. Demographic characteristics and mean follow-up period did not differ between the groups. The incidences of patellar maltracking, erosion, and fractures were investigated. Factors affecting each patellar complication in group D were investigated in terms of age, sex, body mass index, postoperative hip-knee-ankle angle (HKA), remnant patellar thickness, and change in joint line height.

RESULTS

The incidence of patellar maltracking and erosion was significantly higher in group D than in group N [maltracking: 16 (21.1%) vs. 0 cases (0%), p = 0.001; erosion: 30 (39.5%) vs. 2 cases (4.9%), p < 0.001]. The incidence of patellar fractures tended to be higher in group D [6 (7.8%) vs. 0 cases, p = 0.090]. In group D, postoperative valgus limb alignment and younger age were identified as significant factors that affected patellar maltracking (odds ratio of postoperative HKA = 1.628, p = 0.005) and erosion (odds ratio of age = 0.909, p = 0.009), respectively.

CONCLUSION

Close observation of the complications of deficient patellae is required after 1.5-stage exchange arthroplasty. Valgus limb alignment should be avoided to reduce the risk of complications. Early second-stage revision with patellar reconstruction can be considered in younger patients with deficient patellae.

LEVEL OF EVIDENCE

III.

Similar Midterm Outcomes of Total Knee Arthroplasties with Anterior and Posterior Tibial Slopes Performed on Paired Knees at a Minimum Follow-up of 5 Years

A small posterior tibial slope (PTS) is generally recommended in posterior stabilized (PS) total knee arthroplasty (TKA). An unwanted anterior tibial slope (ATS), which can affect postoperative results, may be created in PS TKA because of the inaccuracy of surgical instruments and techniques, as well as high interpatient variability. We compared midterm clinical and radiographic results of PS TKAs with ATS and PTS performed on paired knees using the same prosthesis. One-hundred-twenty-four patients who underwent TKAs with ATS and PTS on paired knees using ATTUNE posterior-stabilized prostheses were retrospectively reviewed after a minimum follow-up period of 5 years. The mean follow-up period was 5.4 years. The Knee Society Knee and Function scores, Western Ontario and McMaster Universities Osteoarthritis Index, Feller and Kujalar scores, and range of motion (ROM) were evaluated. The preferred TKA out of ATS and PTS was also investigated. The hip-knee-ankle angle, component positions, tibial slope, posterior femoral offset, Insall-Salvati ratio, and knee sagittal angle were measured by radiography. There were no significant differences in the clinical results, including ROM, between TKAs with ATS and PTS preoperatively and at the last follow-up. Regarding patient preference, 58 patients (46.8%) were satisfied with bilateral knees, 30 (24.2%) preferred knees with ATS, and 36 (29%) preferred knees with PTS. There was no significant difference in the rate of preference between TKAs with ATS and PTS (p = 0.539). Except for the postoperative tibial slope (-1.8 vs. 2.5 degrees, p < 0.001), there were also no significant differences in the radiographic results, including the knee sagittal angle, preoperatively and at the last follow-up. The midterm outcomes were similar between PS TKAs with ATS and PTS performed on paired knees at a minimum of 5 years of follow-up. Nonsevere ATS did not affect midterm outcomes in PS TKA with proper soft tissue balancing and the current prosthesis of improved design. However, a long-term follow-up study is required to confirm the safety of nonsevere ATS in PS TKA. LEVEL OF EVIDENCE::  III.

Can a Total Knee System Providing 1 mm Increment of Polyethylene Insert Thickness Offer a Clinical Benefit?

Background and Objectives: The purpose of this study was to compare clinical outcomes and polyethylene (PE) insert thickness between total knee arthroplasty (TKA) systems providing 1 mm and 2 mm increments. Materials and Methods: In this randomized controlled trial, 50 patients (100 knees) undergoing same-day or staggered bilateral TKA were randomized to receive a TKA system providing 1 mm increments in one knee (1 mm group) and a TKA system providing 2 mm increments in the other knee (2 mm group). At 2 years postoperatively, Knee Society Score (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, Forgotten Joint Score (FJS), range of motion (ROM), and insert thicknesses were compared between the groups. Results: A total of 47 patients (94 knees) participated in follow-up analysis. In each group, patient-reported outcomes improved significantly after TKA (all, p < 0.05). There were no significant differences in patient-reported outcomes. The mean ROM was not significantly different between groups at preoperative and 2-year points. The rate of postoperative flexion contracture ≥ 5° was 2.1% and 4.3%, and the rate of postoperative recurvatum ≥ 5° was 4.3% and 2.1% in the 1 mm group and 2 mm, respectively (all, p = 1.000). Mean insert thickness was significantly thinner in the 1 mm group than the 2 mm group (p = 0.001). The usage rate of a thick insert (≥14 mm) was 12.7% and 38.3% in the 1 mm group and 2 mm group (p = 0.005). Conclusions: The use of a TKA system providing 1 mm PE insert thickness increments offered no clinical benefit in terms of patient reported outcomes over systems with 2 mm increments at 2 years of follow-up. However, the TKA system with 1 mm increments showed significantly thinner PE insert usage. As a theoretical advantage of 1 mm increments has yet to be proven, the mid- to long-term effects of thinner PE insert usage must be determined.

Aseptic survival of the 1.5-stage exchange arthroplasty for periprosthetic joint infection was acceptable when using an autoclaved femoral component and a new polyethylene insert

PURPOSE

To investigate the aseptic survival of 1.5-stage exchange arthroplasty for periprosthetic joint infection (PJI) after total knee arthroplasty (TKA).

METHODS

Eighty-eight cases of 1.5-stage exchange arthroplasty for PJI without reinfection were retrospectively analysed. The autoclaved femoral component and new polyethylene insert (PE) were implanted using antibiotic mixed cement. The explanted tibial component was not reinserted. The Western Ontario and McMaster Universities Osteoarthritis Index and range of motion were clinically evaluated preoperatively and at the last follow-up (the last time for the implant in situ). Radiographically, hip-knee-ankle angle (HKA) and component positions were measured preoperatively, postoperatively (1 month after the 1.5-stage exchange arthroplasty), and at the last follow-up. The survival rate was analysed using the Kaplan-Meier method, in which failure was defined as reoperation due to aseptic failure. Mean period to failure and failure site were analysed. Factors affecting survival were investigated in terms of demographics and inappropriateness of the postoperative HKA (HKA > 0 ± 3°) and component positions (α angle > 95 ± 3°, β angle > 90 ± 3°, γ angle > 3 ± 3°, and δ angle > 87 ± 3°).

RESULTS

The spacer in-situ time was 3.7 years (0.2-6.4). The clinical results improved hip-knee-ankle significantly at the last follow-up. Radiographically, the average HKA was valgus 0.1° postoperatively. The average α, β, γ, and δ angles of the postoperative component positions were 95.9°, 90.4°, 3.8°, and 86.7°, respectively. The 1-, 2-, and 5-year postoperative survival rates were 90.9%, 86.4%, and 80.6%, respectively. The mean period to failure was 2.0 years (0.2-5.3). There were 18 cases of aseptic loosening (20.8%), occurring on both the femur and tibial sides in 1 knee, and only on the tibial side in 17 knees. Inappropriate coronal position of the PE (β angle > 90 ± 3°) was a significant factor affecting survival (odds ratio = 5.491; p = 0.011).

CONCLUSION

The aseptic survival of the 1.5-stage exchange arthroplasty was acceptable when using an autoclaved femoral component and new PE. The appropriate coronal position of the PE helps ensure favourable survival of 1.5-stage exchange arthroplasty.

LEVEL OF EVIDENCE

IV.

Predictors of Recurrent Flexion Contracture after Total Knee Arthroplasty in Osteoarthritic Knees with Greater Than 15° Flexion Contracture

Background

This study aimed to analyze the risk factors that predict recurrent flexion contracture (FC) after total knee arthroplasty (TKA) in osteoarthritic knees with FC ≥ 15°.

Methods

Data from a consecutive cohort comprising 237 TKAs in 187 patients with degenerative osteoarthritis, preoperative FC ≥ 15°, and a minimum follow-up period of 2 years were retrospectively reviewed. Preoperative FC was corrected intraoperatively from 0° to 5°. The incidence of recurrent FC (FC ≥ 10°) at 2 years postoperatively was investigated. Potential risk factors predicting recurrent FC including age, sex, body mass index, unilateral TKA, severity of preoperative FC, 3-month postoperative residual FC, γ angle, change in posterior femoral offset ratio, and lumbar degenerative kyphosis (LDK) were analyzed using logistic regression analysis. The post-hoc powers for the identified factors were then determined.

Results

Forty-one knees (17.3%) with recurrent FC were identified. Risk factors with sufficient power for recurrent FC were unilateral TKA, severity of preoperative FC, residual FC at 3 months postoperatively, and LDK (odds ratios of 3.579, 1.115, 1.274, and 3.096, respectively; p < 0.05; power ≥ 86.1).

Conclusions

Recurrent FC can occur in TKAs with the risk factors including unilateral TKA, severe preoperative FC, residual FC at 3 months postoperative, and LDK despite appropriate intraoperative correction. Surgical strategies and rehabilitation protocols used in managing FC should be applied in TKA cases with risk factors for recurrent FC.

Computer-based analysis of different component positions and insert thicknesses on tibio-femoral and patello-femoral joint dynamics after cruciate-retaining total knee replacement

BACKGROUND

Positioning of the implant components and tibial insert thickness constitute critical aspects of total knee replacement (TKR) that influence the postoperative knee joint dynamics. This study aimed to investigate the impact of implant component positioning (anterior-posterior and medio-lateral shift) and varying tibial insert thickness on the tibio-femoral (TF) and patello-femoral (PF) joint kinematics and contact forces after cruciate-retaining (CR)-TKR.

METHOD

A validated musculoskeletal multibody simulation (MMBS) model with a fixed-bearing CR-TKR during a squat motion up to 90° knee flexion was deployed to calculate PF and TF joint dynamics for varied implant component positions and tibial insert thicknesses. Evaluation was performed consecutively by comparing the respective knee joint parameters (e.g. contact force, quadriceps muscle force, joint kinematics) to a reference implant position.

RESULTS

The PF contact forces were mostly affected by the anterior-posterior as well as medio-lateral positioning of the femoral component (by 3 mm anterior up to 31 % and by 6 mm lateral up to 14 %). TF contact forces were considerably altered by tibial insert thickness (24 % in case of + 4 mm increase) and by the anterior-posterior position of the femoral component (by 3 mm posterior up to 16 %). Concerning PF kinematics, a medialised femoral component by 6 mm increased the lateral patellar tilt by more than 5°.

CONCLUSIONS

Our results indicate that regarding PF kinematics and contact forces the positioning of the femoral component was more critical than the tibial component. The positioning of the femoral component in anterior-posterior direction on and PF contact force was evident. Orthopaedic surgeons should strictly monitor the anterior-posterior as well as the medio-lateral position of the femoral component and the insert thickness.

Long-term survival of fully cemented stem in re-revision total knee arthroplasty performed on femur with diaphyseal deformation due to implant loosening

PURPOSE

The study aims to analyze long-term clinical and radiographic results, and survival of re-revision total knee arthroplasty (TKA) using fully cemented stems performed on femurs with diaphyseal deformation.

METHODS

Thirty-seven re-revision TKAs using fully cemented stems performed in femoral diaphyseal deformations, characterized as diaphyseal canal enlargement and cortex deformation due to aseptic loosening of previously implanted stems, between 2003 and 2015 were retrospectively reviewed. The mean follow-up period was 10.0 years. Clinically, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and range of motion (ROM) were evaluated. Radiographically, mechanical axis (MA) and component positions were measured. Complications and survival rates were also analyzed.

RESULTS

Clinically, the WOMAC significantly improved at final follow-up (61.2 vs 47.2, p < 0.001), but not the ROM (95.5 vs 102.5, p = 0.206). Radiographically, the MA and component positions were appropriate, with no changes in component positions from immediately post-operative to final follow-up, but with MA change from varus 2.9° to 3.7° (p = 0.020). Two cases (5.4%) with history of previous infections developed periprosthetic joint infection (PJI). Debridement with polyethylene insert exchange following antibiotic suppression were performed in those cases because of concern for difficult implant-cement removal. The five and ten year survival rates were 100% and 93.2%, respectively.

CONCLUSION

Fully cemented stems are viable in providing long-term satisfactory survival after re-revision TKA in patients with femoral diaphyseal deformation. However, it should be used carefully for those with previous infections.

Long-term outcomes were similar between hybrid and cemented TKAs performed on paired knees at a minimum 15 years of follow-up

PURPOSE

To compare long-term clinical and radiographic results and survival rates between hybrid and cemented total knee arthroplasties (TKAs) performed on paired knees.

METHODS

Seventy-two patients with hybrid and cemented TKAs performed on paired knees with NexGen® cruciate-retaining prostheses were retrospectively reviewed after a minimum 15 years of follow-up. Mean follow-up period was 17.5 years. Preoperative alignment deformity and range of motion (ROM) were not different between groups. The Knee Society score, Western Ontario and McMaster Universities Osteoarthritis Index, and ROM were evaluated. Radiographically, change in joint space width, component loosening, and osteolysis were evaluated. Implant survival rate was analyzed.

RESULTS

There were no significant differences in clinical results between hybrid and cemented TKAs performed on paired knees of 72 patients at the last follow-up. No significant difference was observed in the change in joint space width between the two groups at the last follow-up (medial = 0.3 mm vs. 0.4 mm; lateral = 0.1 mm vs. 0.2 mm). One hybrid TKA showed tibial component loosening, for which revision was performed. There was femoral osteolysis in one hybrid and one cemented TKA, and tibial osteolysis in eight hybrid TKAs and seven cemented TKAs (n.s., respectively). The 20-year survival rate was 97.7% for hybrid TKAs and 100% for cemented TKAs (n.s.).

CONCLUSION

The long-term outcomes were similar between hybrid and cemented TKAs performed on paired knees at a minimum 15 years of follow-up. The method of femoral component fixation did not have a significant effect on long-term TKA success.

LEVEL OF EVIDENCE

III.

Mid-flexion laxity could be identified with continuous flexion-arc gap assessment in patients with a large preoperative convergence angle

PURPOSE

To analyze the incidence of intraoperative mid-flexion laxity using continuous flexion-arc gap assessment, risk factors for mid-flexion laxity, and clinical results in navigation-assisted total knee arthroplasty (TKA).

METHODS

Ninety posterior-stabilized TKAs were performed under navigation guidance for patients with degenerative arthritis and varus deformity. Intraoperatively, the gap between the trial femoral component and insert was evaluated in the navigation system with continuous flexion-arc gap assessment. Each medial and lateral gap at flexion (90°) and extension (0°) were made to be less than 3 mm. Mid-flexion laxity was determined when the gap in the flexion range between 15° and 60° was 3 mm or more. The proportion of knees with mid-flexion laxity was investigated. The factors affecting mid-flexion laxity were identified in terms of demographics, preoperative convergence angle, and change in joint line height and posterior femoral offset. The Knee Society Score and Western Ontario and McMaster Universities Osteoarthritis Index were evaluated.

RESULTS

There were 31 cases (34.4%) of lateral mid-flexion laxity (average peak mid-flexion gap = 3.7 mm). The other 59 cases did not show mid-flexion laxity. The preoperative convergence angle was the only significant factor affecting lateral mid-flexion laxity (odds ratio = 1.466, p = 0.002). There were no significant differences in the clinical results between the groups with and without mid-flexion laxity.

CONCLUSIONS

The continuous flexion-arc gap assessment was useful in evaluating mid-flexion laxity using navigation-assisted TKA. The preoperative convergence angle, reflecting soft-tissue laxity, can be a practical and simple radiographic finding for predicting lateral mid-flexion laxity.

LEVEL OF EVIDENCE

IV.

Intraoperative Assessment of Gap Balancing in Total Knee Arthroplasty Using Navigation with Joint Stability Graphs

The purpose of this study was to assess continuous gaps in the replaced knee throughout the full range of motion (ROM) after total knee arthroplasty (TKA) using a joint stability graph, and to analyze the gap laxity in the mid-flexion range. Ninety-three TKAs were performed using imageless navigation with a joint stability graph. While positioning guides for each respective cut, the surgeon can safely preview the resection's impact for the resulting joint gaps and control the soft tissue balance at the knee flexion of 0° (extension) and 90° (flexion). The gaps between the femoral component and insert were evaluated throughout the full ROM using the joint stability graph. The mechanical axis (MA) and change of joint line height were radiographically evaluated. Posthoc power analyses using a significant α value of 0.05 were performed on the proportion of the mid-flexion instability as a primary outcome to determine whether the sample had sufficient power. The power was determined to be sufficient (100%). The flexion-extension gap differences in each medial and lateral compartment and the mediolateral gap differences in flexion and extension were all ≤3 mm. None of the knees had mid-flexion instability, which is defined by a peak mid-flexion gap that is 3 mm greater than the smaller value of flexion or extension gap. The average MA was well corrected from varus 11.4° to varus 1.0° postoperatively. The proportion of postoperative well-aligned knees (MA ≤ 3°) was 87.1%. The joint line height was well preserved (14.7 vs. 14.8 mm, p = 0.751). The joint stability graph in TKA using the navigation can effectively evaluate the continuous gap throughout the ROM, including the mid-flexion range. Mid-flexion instability was uncommon in primary TKAs with appropriate alignment and proper preservation of the joint line. The Level of evidence for the study is IV.

Comparison of risk for postoperative hyperextension between cruciate retaining and posterior stabilized total knee arthroplasties

INTRODUCTION

The incidence of postoperative hyperextension and factors affecting hyperextension needs to be investigated separately for cruciate retaining (CR) and posterior stabilized (PS) total knee arthroplasties (TKAs), because the mechanism for preventing hyperextension is different according to the bearing design. The purpose of the study was to compare the incidence of postoperative hyperextension between CR and PS TKAs and analyze the factors affecting the postoperative hyperextension.

METHODS

Matched 213 CR and PS TKAs with Persona^® prosthesis were retrospectively reviewed. The preoperative demographics, clinical and radiographic knee condition, and pelvic incidence were similar between groups. Appropriate knee extension (0°-5°), confirmed with a goniometer, was achieved intraoperatively. The knee sagittal angle was radiographically measured preoperatively and at 2 years postoperative. The incidence of hyperextension (sagittal angle < - 5°) was investigated. The factors affecting the postoperative hyperextension were analyzed in terms of age, sex, preoperative mechanical axis, knee sagittal angle, postoperative posterior tibial slope (PTS), change of posterior femoral offset, and pelvic incidence.

RESULTS

The knee sagittal angle was not significantly different preoperatively between CR and PS TKAs. The postoperative knee sagittal angle was 2.9° in CR TKAs and 4.4° in PS TKAs (p = 0.004). The incidence of postoperative hyperextension was 11.7% (25/213) in CR TKAs and 4.2% (9/213) in PS TKAs (p = 0.007). The preoperative sagittal angle, postoperative PTS, and pelvic incidence were the significant factors affecting the postoperative hyperextension in CR TKAs (odds ratio 0.869, 2.205, and 1.045, respectively); the preoperative sagittal angle was only the significant factor in PS TKAs (odds ratio 0.857) CONCLUSIONS: Postoperative knee hyperextension occurred more frequently and was affected by more factors in CR TKAs than PS TKAs. Efforts to avoid hyperextension and closed observation are required in TKAs performed in patients with the risk factors.

LEVEL OF EVIDENCE

III.

Mid-term lifetime survivals of octogenarians following primary and revision total knee arthroplasties were satisfactory: a retrospective single center study in contemporary period

Background

As life expectancy increases, the number of octogenarians requiring primary and revision total knee arthroplasty (TKA) is increasing. Recently, primary TKA has become a common treatment option in octogenarians. However, surgeons may still be hesitant about performing revision TKA on octogenarians because of concern about risk and cost benefit. The purpose of this study was to investigate clinical outcomes, postoperative complications, and mid-term lifetime survival in octogenarians after primary and revision TKA.

Materials and methods

We retrospectively reviewed 231 primary TKAs and 41 revision TKAs performed on octogenarians between 2000 and 2016. The mean age of patients undergoing primary TKA was 81.9 years and that of patients undergoing revision TKA was 82.3 years (p = 0.310). The age-adjusted Charlson comorbidity index was higher in revision TKA (4.4 vs. 4.8, p = 0.003). The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and range of motion (ROM) were evaluated. The incidence of postoperative complications (TKA-related, specific or systemic) and lifetime survival rate (endpoint death determined by telephone or mail communication with patient or family) were investigated.

Results

The WOMAC and ROM improved significantly after primary and revision TKA, although postoperative results were worse in the revision group (33.1 vs. 47.2; 128.9° vs. 113.6°; p < 0.001, respectively). There were no cases of aseptic or septic component failure in either group. One case of periprosthetic fracture was observed in the revision group (0% vs. 2.4%, p = 0.151), and three cases of deep vein thrombosis (DVT)/pulmonary thromboembolism (PTE) (one case of DVT and two cases of PTE) were observed in the primary group (1.3% vs. 0%, p = 1.000). The most common systemic complication in both groups was delirium (7.4% vs. 14.6%, p = 0.131). There were no differences between the two groups in the other systemic complication rates. The 5-year and 10-year lifetime survival rates were 87.2% and 62.9%, respectively, in primary TKA and 82.1% and 42.2%, respectively, in revision TKA (p = 0.017).

Conclusions

Both primary and revision TKA are viable options for octogenarians, based on the satisfactory clinical outcomes, TKA-related complication rates, and mid-term lifetime survival. Delirium needs to be managed appropriately as the most common systemic complication in both primary and revision TKA in octogenarians.

Level of evidence

IV