The contribution of intraoperative medial compartment stability to post-operative knee flexion angle in unicompartmental knee arthroplasty

Different intraoperative joint laxity patterns do not impact clinical outcomes in robotic-assisted medial unicompartmental knee replacement with 1-to-1 surface reconstruction

PURPOSE

Robotic-assisted technology in medial unicompartmental knee arthroplasty (mUKA) allows for customized adjustments of joint laxity through virtual preoperative component positioning before bone preparation. Nevertheless, the optimal balancing curve has yet to be delineated. This study sought to investigate if varying intraoperative knee laxity patterns had any impact on postoperative patient outcomes.

MATERIALS AND METHODS

A retrospective analysis was conducted on prospectively collected data from 326 fixed-bearing RAUKA procedures performed between 2018 and 2022 with a minimum 2-year follow-up. Patients were categorized into three cohorts based on intraoperative joint laxity patterns (millimetres of joint gap during valgus stress) imparted at 20°, 60°, 90° and 120° of knee flexion: cohort 1 < +0.5 mm (tight); cohort 2 between 0.6 and 1.9 mm (physiologic); cohort 3 > 2 mm (loose). Wilcoxon and Kruskal-Wallis tests were conducted to assess patient-reported outcome measure (PROM) improvements and preoperative and postoperative differences across the cohorts. A Spearman's test evaluated the correlation between knee balance at all degrees of flexion and preoperative and postoperative HKA.

RESULTS

No differences in preoperative and postoperative PROMs were identified across the cohorts (p > 0.05). All three cohorts with different joint laxity patterns showed a significant improvement in the postoperative PROMS (p < 0.05). The preoperative or postoperative limb alignment did not significantly affect clinical outcomes relative to different laxity patterns.

CONCLUSION

No differences were found in the outcomes across different joint laxity patterns in robotic-assisted medial UKA using fixed-bearing mUKAs. There was no evident advantage for maintaining a closer to physiologic laxity compared to tighter or looser balancing.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Isolated aseptic loosening in total knee arthroplasty: a comprehensive 10-year review of partial vs. total component revisions

BACKGROUND

In total knee arthroplasty (TKA), isolated aseptic loosening (IAL) requires the replacement of prosthetic components, with ongoing debate regarding the effectiveness of partial component revision (PCR) compared to total component revision (TCR). This study aims to compare implant survival and surgical outcomes between PCR and TCR in the context of IAL.

METHODS

This retrospective study analyzed data from 285 patients who underwent revision TKA for IAL between January 2000 and December 2013. After applying exclusion criteria, 112 patients were included in the analysis-60 undergoing TCR and 52 undergoing PCR.

RESULTS

PCR was associated with shorter operative times and hospital stays compared to TCR, alongside significant differences in the choice of revision prostheses. Although the prosthesis failure rates were comparable between the groups (13.6% for TCR and 18.33% for PCR), significant risk factors for failure were identified, including a canal filling ratio (CFR) below 0.8 and a discrepancy over 0.2 between CFR views. However, no significant differences in overall survivorship were observed between the groups.

CONCLUSIONS

Both PCR and TCR provide similar survival rates and clinical outcomes for managing IAL in TKA. PCR provides advantages in terms of surgical efficiency and patient recovery, while reducing the need for more constrained prosthetic solutions. The study identifies CFR as a critical predictor of prosthesis failure, highlighting the importance of detailed preoperative planning and implant selection. These findings contribute valuable insights for improving revision strategies in IAL, enhancing surgical outcomes in TKA.

LEVEL OF EVIDENCE

III.

Propensity of the tight mid-flexion and loose flexion gap despite the adjustment of extension and flexion gaps in Oxford unicompartmental knee arthroplasty: retrospective study

PURPOSE

A well-balanced joint gap is necessary in Oxford unicompartmental knee arthroplasty (OUKA) to prevent mobile-bearing dislocation. While the gaps between 20° (extension) and 100° (flexion) are precisely adjusted using the incremental mill system, there has been insufficient evaluation of gaps in other angles. We hypothesized that the gap is not always the same in other angles. This retrospective study aimed to evaluate the gap in full-extension (0°), mid-flexion (60°) and deep flexion (130°) for comparison with those in extension and flexion gaps.

METHODS

We evaluated 119 knees in 83 patients (51 females, 31 males, aged 71.9 years). The full-extension and mid-flexion gaps were compared with the extension gap, and the deep flexion gap was contrasted with the flexion gap. Each gap was classified into isometric, tight or loose, for evaluation of contributing factors.

RESULTS

Although the full-extension gap tended to be isometric (45%), the mid-flexion tended to be tight (48%), whereas the deep-flexion was loose in most knees (84%) (P = 0.002). The tight mid-flexion and loose deep flexion gap pattern accounted for 44% of the total knees, especially so with smaller femoral components (P = 0.004).

CONCLUSION

Our results highlight the propensity of tight mid-flexion and loose flexion gap despite the adjustment of extension and flexion gaps in OUKA. Although the effect of such a minor gap imbalance is still unknown, the pattern was more prevalent in patients with smaller-sized femoral components. Use of a larger femoral component may equalize the gap throughout the motion arc.

Preoperative varus deformity of the knee affects the intraoperative joint gap in unicompartmental knee arthroplasty

BACKGROUND

It is generally believed that contraction of the soft tissue structures on the medial side may occur in the knee with severe varus deformity. However, the relationship between the severity of varus deformity of the knee and the intraoperative soft tissue balance in unicompartmental knee arthroplasty (UKA) has not been well reported thus far.

METHODS

One hundred and three consecutive medial UKAs were enrolled. After the femoral trial prosthesis was placed, the component gap was measured at 10° (extension) and 120° (flexion) of flexion using a UKA tensor. The pre-osteotomy gap was then calculated from the thickness of the bone cut. Paired Student's t-test was used to compare the component gap, as well as the pre-osteotomy gap, in extension and those in flexion. The relationship between the preoperative Hip-Knee-Ankle (HKA) angle and the pre-osteotomy gap was analysed using Pearson's correlation coefficient and simple linear regression analysis.

RESULTS

The component gap in extension was significantly smaller than that in flexion while the pre-osteotomy gap in extension was significantly wider than that in flexion. There was a positive correlation between the severity of varus deformation in preoperative knee and the pre-osteotomy gap in extension, while there was no correlation between the preoperative HKA angle and the pre-osteotomy gap in flexion.

CONCLUSIONS

The tension of the medial tightness does not correlate with the degree of preoperative varus deformity in UKA.

Appropriate Timing for Evaluation of the Short-Term Effectiveness of Unicompartmental Knee Arthroplasty

Satisfactory results have been achieved with unicompartmental knee arthroplasty (UKA) for the treatment of isolated unicompartmental knee disease. However, UKA is associated with a significantly higher rate of revision. There is a tendency toward early revision of UKA for persistent pain because surgeons are not aware that outcomes can spontaneously improve with time. The aim of this study was to identify the time period that patients achieved the highest clinical outcomes following UKA. In total, we examined 72 knees that underwent Oxford UKA. We evaluated the range of motion and clinical results including Knee Society Knee Score, Knee Society Function Score (KSFS), and patient-reported scores using the Knee injury and Osteoarthritis Outcome Score (KOOS) at 1, 2, and 3 years postoperatively. The extension angle showed significant recovery from 1 to 2 years postoperatively, but no significant recovery was observed between 2 and 3 years. The flexion angle at 2 years is larger than at 1 year. The KSFS at 3 years is significantly lower than that at 1 year. The KOOS subscale of activities of daily living showed no significant differences among three periods after operation. The subscales of pain, symptom, sports, and quality of life showed significant recovery from 1 to 2 years postoperatively, but no significant recovery was observed from 2 to 3 years. To evaluate the effectiveness of Oxford UKA, surgeons should obtain clinical outcomes 2 years after the operation.

Intraoperative rotational kinematics and its influence on postoperative clinical outcomes differ according to age in Unicompartmental knee Arthroplasty

Background

Although Oxford unicompartmental knee arthroplasty (UKA) is used in patients of wide age ranges, there is no clear information regarding the age differences in terms of intraoperative femorotibial rotational kinematics and its influence on clinical outcomes. Therefore, this study was conducted to examine the age differences in terms of intraoperative rotational kinematics and postoperative clinical outcomes and to analyze their relationship with classification according to the age group.

Methods

We investigated 111 knees of patients who underwent Oxford UKA using a navigation system and divided them into two groups: elderly (aged ≥75 years; 48 knees) and nonelderly (aged < 75 years; 63 knees). Intraoperative tibial internal rotational angles relative to the femur during passive knee flexion were measured using a navigation system, and clinical outcomes were evaluated using knee range of motion, the Knee Injury and Osteoarthritis Outcome Score (KOOS), and the Knee Society Functional Score at 2 years postoperatively. The relationships between intraoperative tibiofemoral rotational angles and clinical outcomes were also evaluated in the two groups.

Results

The intraoperative tibial internal rotational angle relative to the femur during knee flexion was significantly larger in the nonelderly group (13.5°) than in the elderly group (9.0°). The intraoperative tibial internal rotational angle showed a positive correlation with the pain subscale of KOOS only in the nonelderly group.

Conclusion

Intraoperative rotational kinematics and its influence on clinical outcomes were different between elderly and nonelderly patients, and the tibial internal rotational angle could be a more important factor for successful UKA in nonelderly patients.

The medial tibial joint line elevation over 5 mm restrained the improvement of knee extension angle in unicompartmental knee arthroplasty

PURPOSE

The purpose of this study was to examine the relationship between medial tibial joint line elevation and the improvement of range of motion (ROM) in unicompartmental knee arthroplasty (UKA). The hypothesis was that limited elevation of tibial joint line will improve knee range of motion in UKA.

METHODS

Forty-six consecutive medial UKAs were enrolled in this study. Medial tibial joint line elevation was defined as the polyethylene insert and tibial tray thickness minus the tibial osteotomy and sawblade thickness. Positive values indicated an elevation of the tibial joint line. A component gap between the femoral trial prosthesis and the medial tibial osteotomy surface was also examined. Joint loosening was also calculated based on the joint component gap minus insert and tibial tray thickness. The correlation of the medial tibial joint line elevation with joint looseness and postoperative range of motion were analyzed.

RESULTS

The mean medial tibial joint line elevation was 4.9 ± 1.1 mm. The medial tibial joint line elevation reduced the improvement of knee extension (R = - 0.43, p < 0.01). The medial tibial joint line elevation was also correlated with reduced loosening of the joint knee extension (R = - 0.42, p < 0.01). This, in turn, resulted in limited improvement of the knee extension angle. Moreover, joint line elevation under 5 mm significantly improved knee extension angle compared to joint line elevation over 5 mm.

CONCLUSIONS

The medial joint line elevation of the tibia in UKA reduced the improvement of knee extension angle, due to a reduced joint looseness at knee extension. A tibial joint line elevation greater than 5 mm in UKA should be avoided to prevent postoperative flexion contracture. For the clinical relevance, this study clarified that the medial joint line of the tibia is an important factor to prevent postoperative flexion contracture in UKA.

LEVEL OF EVIDENCE

II.

The influence of posterior tibial slope changes on joint gap and range of motion in unicompartmental knee arthroplasty

BACKGROUND

The effect of posterior slope on joint gap in unicompartmental knee arthroplasty (UKA) has yet to be quantified. The purpose of this study was to quantify the effect of the tibial slope on the joint component gap and postoperative range of motion in UKA.

METHODS

Forty consecutive patients were prospectively enrolled. The correlation between the tibial slope changes and the component gap, the component gap difference between flexion angles, the postoperative extension or flexion angles was examined. The correlation of joint looseness with tibial slope changes and postoperative extension angle was also examined.

RESULTS

Increased tibial slope positively correlated with the differences between the component gap at 90° and 10°, 120° and 10°, or 135° and 10° knee flexion angle. Although tibial slope change did not affect postoperative flexion angle, increased tibial slope reduced postoperative extension angle. Moreover, increased tibial slope resulted in decreased joint looseness during 10° of knee flexion and decreased joint looseness during 10° of knee flexion resulted in reduced postoperative extension angle.

CONCLUSIONS

Increased tibial slope resulted in tight component gap at knee extension compared with that at knee flexion. Furthermore, tight component gap at extension lead to decreased postoperative extension angle. These results indicate that an individual anatomical tibial slope should be considered when tibial sagittal osteotomy was performed and increasing tibial slope should be avoided to achieve full extension angle after UKA.

LEVEL OF EVIDENCE

II.