Less polyethylene wear in monobloc compared to modular ultra-high-molecular-weight-polyethylene inlays in hybrid total knee arthroplasty: A 5-year randomized radiostereometry study

Mid-term radiographic evaluation of a monoblock trabecular metal tibia following total knee arthroplasty in obese and morbidly obese patients

BACKGROUND

Indications for primary total knee arthroplasty (TKA) have become more inclusive of morbidly obese patients, however, higher rates of complications and lower implant survival have also been reported in this population. The purpose of this study was to investigate the mid-term survival, clinical, and radiographic outcomes of a cementless trabecular metal monoblock tibial component in severely obese patients.

METHODS

This was a retrospective study of class II and III obese (BMI > 35) patients who received a cementless primary TKA. Standing radiographs were assessed for the presence of progressive tibial radiolucent lines (RLL), and clinical measures were assessed at least 2 years post-operative via the Oxford Knee Score (OKS), UCLA Activity and Satisfaction Score, and the Euro-QoL 5-dimension (EQ-5D-5L) index and visual analogue scale (EQ-VAS) health status.

RESULTS

Patients (n = 176) were 61.2 ± 8.3 years of age, BMI 44.9 ± 6.5 kg/m2, and were predominantly female (n = 118, 66.7%). Mean follow-up was 59.2 ± 17.1 months. There were two total revisions at 6- and 57-months post-operative, respectively, and the 5-year survival estimate was 98.3% (95% confidence interval: 93.0%, 99.6%). Patient satisfaction was 93.9% and the post-operative OKS, EQ-5D-5L index, and EQ-VAS were 40.2 ± 7.9, 0.856 ± 0.205, and 73.6 ± 14.7, respectively. No cases of radiolucent lines were detected.

CONCLUSIONS

At 6 years this cementless monoblock tibial component demonstrated excellent survival without radiographic indications of aseptic loosening in a population of severely obese patients.

6-month migration sufficient for evaluation of total knee replacements: a systematic review and meta-analysis

BACKGROUND AND PURPOSE

This updated meta-analysis evaluates the migration pattern of the tibial component of primary total knee replacements measured with radiostereometric analysis (RSA). We aimed to evaluate whether 6-month maximum total point motion (MTPM) values could be used instead of 1-year MTPM for RSA threshold testing and to present the pooled migration patterns for different implant designs that can be used as a benchmark.

PATIENTS AND METHODS

The search included all published RSA studies on migration patterns of tibial components until 2023. Study groups were classified according to their prosthesis brand, fixation, and insert (PFI). Sub-analyses were performed to compare the mean tibial component migration patterns of different implant variables, stratified according to fixation.

RESULTS

96 studies (43 new studies), including 197 study groups and 4,706 knees, were included. Most migration occurred within the first 6 postoperative months (126 study groups: mean 0.58 mm, 95% confidence interval [CI] 0.50-0.65), followed by minimal migration between 6 and 12 months (197 study groups: mean 0.04 mm, CI 0.03-0.06), irrespective of the fixation method used. Distinct migration patterns were observed among the different fixation methods. No differences were found in migration patterns among cemented components in any of the sub-group analyses conducted. For uncemented implants, trabecular metal surfaced components seemed to migrate less than porous-coated or uncoated components Conclusion: Based on the small difference between MTPM values at 6 months and 1 year, MTPM at 6 months could be used instead of MTPM at 1 year for RSA threshold testing. The pooled migration patterns can be used as benchmark for evaluation of new implants by defining fixation-specific RSA thresholds when combined with implant survival.

The influence of radiologic bone transparency after hybrid total knee arthroplasty on clinical outcomes: Minimum 6-year follow up of 214 cases

BACKGROUND

This study aimed to investigate how bone transparency affects loosening of the cementless femoral component by serially analyzing radiologic images in hybrid total knee arthroplasty (TKA).

METHODS

A total of 214 cases of TKA performed using the hybrid technique that were followed up for at least 6 years were retrospectively investigated. Bone transparency around the femoral component during the follow up period was evaluated. All TKA cases were divided into two groups and compared: those with radiologic bone transparency (bone transparency group, n = 51) and those without radiologic bone transparency (no bone transparency group, n = 163).

RESULTS

The incidence of revision TKA in all patients was 6.1%, and obesity, preoperative and postoperative mechanical alignment did not affect surgical outcomes. All bone transparency cases were asymptomatic, and only 8/51 cases (15.7%) of bone transparency spontaneously resolved. Between the bone transparency and no bone transparency groups, there was no difference found in the preoperative and postoperative radiologic parameters and clinical outcomes. During the follow up period, there were four (1.9%) cases with a definite radiolucent line in the femoral component, all of which belonged to the bone transparency group.

CONCLUSIONS

The bone transparency around the femoral component that appears on radiography after hybrid TKA could be an early sign of aseptic loosening; therefore, follow up serial radiography is essential.