A new method for evaluation of patellar height and the position of the joint line before and after total knee arthroplasty

The ROSA knee robotic system demonstrates superior precision in restoring joint line height and posterior condylar offset compared to conventional manual TKA: a retrospective case-control study

PURPOSE

Variations in total knee arthroplasty (TKA) joint line height may lead to complications such as pain and altered joint mechanics, while posterior condylar offset (PCO) can influence knee stability.

METHODS

Single-centre, single-surgeon retrospective analysis from December 2019 to May 2023 investigated primary unilateral TKA (Nexgen Legacy, Zimmer Biomet) in patients with knee osteoarthritis, using ROSA robotic system (raTKA) or conventional manual technique (mTKA). Joint line height and PCO were measured and compared in 182 raTKA and 144 mTKA patients.

RESULTS

The groups were matched in age (p = 0.847) and sex distribution (p = 0.2). Excellent interobserver agreement (ICC ≥ 0.9). RaTKA mean joint line height difference was - 0.0001 mm (± 3.48, 95% CI - 0.509, 0.509) (p = 0.523), - 0.951 mm for mTKA (± 4.33, 95% CI - 1.664, - 0.237) (p = 0.009). RaTKA mean PCO difference was 0.52 mm (± 2.45, 95% CI 0.160, 0.880) (p = 0.005), 1.15 mm for mTKA (± 4.01, 95% CI - 1.496, 1.818) (p < 0.001). Mean difference in joint line height of 0.95 mm between groups was significant (p = 0.027), and for PCO, it was 0.63 mm, demonstrating tendency towards significance (p = 0.08). Mean absolute value in joint line height difference between groups was not significant (p = 0.235) but highly significant for PCO (p < 0.001).

CONCLUSION

The ROSA knee robotic system can more accurately restore joint line height and PCO compared to conventional manual TKA. The improved degree of precision raTKA offers may be a vehicle for better Patient-Reported Outcome Measures, but further correlational studies are required.

Joint line position change in primary total knee arthroplasty: a radiographic analysis comparing conventional and robotic techniques

PURPOSE

Joint line (JL) position change in total knee arthroplasty (TKA) may alter knee biomechanics and impact function. The purpose of this study was to compare the change in JL position between robotic-assisted TKA (RA-TKA) and conventional TKA (C-TKA).

METHODS

A retrospective, radiographic analysis was conducted of patients who underwent RA-TKA and C-TKA to compare JL position change. JL position was measured in consecutive RA-TKAs and C-TKAs performed by four fellowship-trained arthroplasty surgeons. Statistical analysis was done utilizing t-tests and Mann Whitney U tests, with statistical significance being defined as a p value < 0.05.

RESULTS

Six hundred total RA-TKAs and 400 total C-TKAs were included in the analysis. There were no significant differences in patient baseline characteristics such as body mass index, range of motion, and tibiofemoral coronal alignment. RA-TKAs were associated with an average of 0.04 (2.2) mm JL position change, and C-TKAs were associated with an average 0.5 (3.2) mm JL position change (p = 0.030). There were inter-surgeon differences when comparing the change in JL position for RA-TKAs and C-TKAs between the four participating surgeons.

CONCLUSION

RA-TKA leads to better preservation of the JL position than C-TKA, and this seems to be dependent on the arthroplasty surgeon's preferences and techniques during TKA. Whether this statistically significant difference is clinically relevant needs to be further investigated.

Acquired changes in thickness and length of patellar tendon after primary total knee arthroplasty: a prospective ultrasonographic study with over 4 years of follow-up

Previous literature has reported changes in the length or thickness of the patellar tendon (PT) following primary total knee arthroplasty (TKA). This study aims to determine the structural changes in both the length and thickness of the PT after primary TKA using ultrasound (US) and to investigate the association between these changes and clinical outcomes after a minimum follow-up of 48 months. This prospective study used the US on 60 knees of 32 patients (aged 54-80, mean 64.8±7 years) before and after primary TKA to evaluate changes in both the length and thickness of the patellar tendon. Clinical outcomes were assessed with HSS and Kujala scores. At the latest follow-up evaluation, there was a significant overall shortening of PT by 9.1% (p<0.001), in addition to significant global thickening by 20% (p<0.001). Besides, there was significant thickening by 30% in the proximal 1/3 (p<0.01) and 27% in the middle 1/3 (p<0.01) segments of PT. There was a significant negative correlation between the thickening identified in all three parts of the tendon and both clinical outcome measures (p<0.05). The results show the presence significant changes in PT in terms of length and thickness after primary TKA; in addition, increased thickness in PT was more strongly and significantly associated with inferior clinical outcomes, including functionality and anterior knee pain, than shortness in PT. This study also suggests that the US is a viable, non-invasive method for documenting PT changes in both length and thickness after TKA with serial scans.

Evaluation of the flexion gap with a distal femoral trial component in posterior-stabilized total knee arthroplasty

Purpose

A distal femoral trial component was manufactured, and flexion gap size and inclination were evaluated with or without the distal femoral trial component in total knee arthroplasty (TKA). This study aimed to evaluate the effect of the distal femoral trial component on flexion gap size and joint inclination in posterior-stabilized (PS)-TKA.

Materials and methods

A total of 84 patients with medial osteoarthritis who underwent mobile-bearing PS-TKA using modified gap techniques were included in this retrospective study. The flexion gap size and inclination before and after setting the distal femoral trial component were evaluated and compared with the final gap size and inclination.

Results

The joint gap size and inclination were significantly lower in those with than in those without the distal femoral trial component (P = 0.005, P < 0.001). The final gap size and inclination were similar to the gap size and inclination with the distal trial component (P = 0.468, P = 0.158).

Conclusions

The joint gap size and medial tension in PS-TKA were significantly reduced after setting the distal femoral trial component. The flexion gap measured using the distal femoral trial component was similar to that when the final trial component was set. To more accurately perform the gap technique TKA, the flexion gap should be measured using the distal femoral trial component.

Patellar height after unicompartmental knee arthroplasty: comparison between fixed and mobile bearing

PURPOSE

The purpose of this study was to determine the changes in patellar heights by comparing standardised pre- and post-operative radiographs in a consecutive series of patients undergoing unicompartmental knee arthroplasty (UKA) with two different approaches and implant designs [fixed bearing (FB) vs mobile bearing (MB)] and to correlate the patellar heights with clinical outcomes.

METHODS

One hundred and seventy-two UKA patients were prospectively enrolled in the study. 75 patients underwent a minimally invasive FB medial UKA (referred to hereinafter as the 'FB group'); 97 patients were treated with a minimally invasive MB medial UKA. The pre-operative and mid-term (1-year) post-operative patellar heights and clinical scores of these groups of patients were compared using the Insall-Salvati (IS) and Caton-Deschamps (CD) indices and the Oxford Knee Score (OKS).

RESULTS

No differences were found between the two groups either with regard to the pre-operative data (p > 0.05) or between pre- and post-operative radiographic scores at the time of each follow-up (p > 0.05). Both the groups reported a significant clinical improvement (p<0.05) as did all the sub-groups (p < 0.05). In the MB group, a higher CD index in females was found at the final follow-up stage (p = 0.043) and a higher pre-operative CD index was found in patients with BMI ≥ 28 (p = 0.040). A statistically negative correlation was found between the pre-operative OKS and pre-operative IS index (rho=- 0.165; p=0.031).

CONCLUSIONS

Both FB and MB arthroplastys with different surgical approaches did not change the patellar height regardless of the age, gender and BMI at short-medium-term follow-up. The post-operative patellar height seems not to be correlated with the clinical outcomes. A higher pre-operative IS index was correlated with knee pain and function.

LEVEL OF EVIDENCE

Level II-prospective comparative study.

STUDY REGISTRATION

Researchregistry6433- www.researchregistry.com .

Evaluation of patella height in native knees and arthroplasty: an instructional review

Total knee arthroplasty (TKA) is the gold standard for treating advanced knee osteoarthritis. Among the postoperative complications of TKA are true patella infera (TPI) and pseudo patella infera (PPI), which should be differentiated since TPI exhibits significantly worse clinical outcomes. Multiple radiological patella height indices (PHI) exist; some were modified or originally designed for knees with implanted endoprostheses. However, there is no consensus on measuring and comparing patella height. Due to the lack of established, simple, reliable, and reproducible concepts for assessing patella height for arthroplasty, measuring patella height and the change of patella height by or after TKA have been challenging tasks for clinicians and researchers. This is a review of the current literature on methods for measuring patella height, with special attention to the ability to differentiate between the TPI and PPI after TKA. All literature on the topic was retrieved, and references from relevant articles were investigated until the end of April 2022.