Body mass index changes after unicompartmental knee arthroplasty do not adversely influence patient outcomes

Evaluating the Minimum Clinically Important Difference and Patient Acceptable Symptom State for the Womac Osteoarthritis Index after Unicompartmental Knee Arthroplasty

Patient-Reported Outcome Measures (PROMs) are standardized questionnaires that gather information on health-related quality of life directly from patients. Since a significant statistical mean change may not correspond to a clinical improvement, there is a need to calculate a considerable change in scores. This is done by the Minimum Clinically Important Difference (MCID) and Patient Acceptable Symptom State (PASS). The objective of this article is to report the MCID and the PASS values of the WOMAC (Western Ontario and McMaster University) osteoarthritis index for patients undergoing Unicompartmental Knee Arthroplasty (UKA). A total of 37 patients (25 females and 12 males; mean age 68 ± 8.1 years and mean BMI 28.7 ± 4) who underwent UKA were enrolled. All patients were assessed using the WOMAC and the Oxford Knee Score (OKS) questionnaires before and six months following the procedure. To measure the cut-off values for MCID, distribution methods and anchor methods were applied, while the PASS was assessed only via anchor approaches. The MCID related to the WOMAC average global score was 90.7 ± 7.6, the average pain dimension score was 93.2 ± 6.6, the average stiffness dimension score was 92.6 ± 17, and the average physical function dimension score was 89.7 ± 7.6. In terms of PASS, the normalized WOMAC was 82.8, the pain dimension was 87.5, the stiffness dimension was 93.7, and the functional dimension was 83.1. A 34.5 amelioration in the WOMAC score, from initial evaluation to final follow-up, using change in OKS > 5 as anchor, indicates that the patients' health state improved to a clinically significant degree. A value at least of 82.8 in WOMAC score after treatment denotes that the symptom state is deemed acceptable by most of the patients.

The impact of preoperative MRI-detected lateral meniscal intra-substance signal abnormalities on mid-term functional outcomes following mobile-bearing unicompartmental knee arthroplasty

PURPOSE

There is a dilemma as to whether the presence of degenerative changes of lateral meniscus is a contraindication to medial unicompartmental knee arthroplasty (UKA). Therefore, the purpose of this study is to assess the influence of preoperative MRI-detected lateral meniscal intra-substance signal abnormalities on mid-term functional outcomes following mobile-bearing UKA.

METHODS

We performed a retrospective review of the record on a consecutive series of patients who have undergone mobile-bearing medial UKA from September 2020 to June 2023. The mean duration of follow-up was 2.34 years. All records were collected from case system. MRI assessment of lateral meniscus was performed with the use of the Stoller's classification system. Patients were categorized into two groups (grade 0 and ≥ grade 1). Patient-reported outcomes were assessed with the use of the American Knee Society functional Score (AKSS-F), American Knee Society Objective Score (AKSS-O), and Oxford Knee Score (OKS) preoperatively and at latest follow-up. Furthermore, range of motion (ROM) and hip-knee-ankle angle (HKA) were measured in preoperative and postoperative periods.

RESULTS

A total of 92 patients (101 knees) were included in our study. No differences in AKSS-F, AKSS-O, OKS, HKA, or ROM were found between those who showed normal or abnormal signal change of lateral meniscus preoperatively (P < 0.05). Furthermore, there were also no significant differences between two groups concerning AKSS-F, AKSS-O, OKS, HKA, or ROM at latest postoperative follow-up (P < 0.05). Age and duration of disease were independent predictors of low postoperative AKSS-F and AKSS-O (P < 0.05). Nevertheless, ROM was an independent predictor of high postoperative AKKS-O (P < 0.05). Age and female were independent predictors of high postoperative OKS (P < 0.05).

CONCLUSION

The presence of preoperative MRI-detected lateral meniscal degenerative changes did not affect mid-term functional outcomes in patients who underwent mobile-bearing medial UKA. On the basis of the results of the current study, we believe that the presence of degenerative changes of lateral meniscus is acceptable in mobile-bearing medial UKA.

Obesity increases the risk of conversion to total knee arthroplasty after unicompartimental knee arthroplasty: a meta-analysis

PURPOSE

The aim of this meta-analysis was to to determine the influence of obesity on patient outcome and implant survivorship after primary unicompartmental knee arthroplasty (UKA).

METHODS

A PRISMA systematic review was conducted by searching the Medline (PubMed), EMBASE, and Cochrane electronic databases to identify clinical studies investigating the effect of obesity on outcomes after UKA. Data were collected on aspecifically designed extraction form. Methodological quality was assessed using the Methodological Index for Nonrandomized Studies score. Quantitative meta-analysis was carried out using RevMan 5.4 software.

RESULTS

A total of 17 studies were included; 43,845 primary UKA patients were classified by their BMI: on-obese (BMI 25 to < 30 kg/m²); obese (BMI 30 to < 35 kg/m²); severely obese (BMI > 35 kg/m²). Pooled analysis showed no statistically significant difference in Knee Society Score (KSS) pain in the obese (n.s.) and the severely obese (n.s.) group compared to the non-obese group, while the KSS function score was lower in the severely obese (P = 0.0002) compared to the obese (P = 0.06) and the non-obese group. Postoperative Oxford Knee Score (OKS) was lower in the obese group (P = 0.01) but not in the severely obese group (P = 0.16). Postoperative Range of Motion (ROM) was comparable in the obese and non-obese group (P = 0.16). Implant survival at 10 years follow-up was significantly lower in the obese (82.5-95.3%; P < 0.0001) and the severely obese group (87.5-93.8%; P < 0.0001) thanthe non-obese group (83.6-98.6%).

CONCLUSION

Obesity and severe obesity were associated with significantly higher revision and lower implant survival rates. Obesity did not influence clinical and most functional outcomes after UKA, whereas KSS function score was significantly lower only for the severely obese patient group.

LEVEL OF EVIDENCE

III, meta-analysis.

Return to physical activity and change in body mass index after hypoallergenic medial mobile-bearing unicompartmental knee arthroplasty

Background

The primary purpose of the present prospective study was to consecutively analyse the outcomes of the return to sports activity of patients with positive patch tests undergoing a medial mobile-bearing titanium niobium nitride (TiNbN) unicompartmental knee arthroplasty (UKA). The secondary purpose was to ascertain if a higher grade of physical activity leads to a reduction in the body mass index (BMI) of the patients.

Material and methods

Forty-one patients with positive skin patch tests were included in this prospective study. The clinical evaluation consisted of the University of California, Los Angeles (UCLA) activity scale and the High-Activity Arthroplasty Score (HAAS). Each patient was evaluated the day before surgery (T₀), after 12.37 ± 0.70 months (T₁), and on the day of the final follow-up, after 67.03 ± 18.2 months (T₂). Furthermore, the BMI of each patient was analysed before surgery and during the final follow-up.

Results

The UCLA and HAAS mean preoperative values ranged from 3.68 ± 1.1.7 and 6.15 ± 0.76 to 6.1 ± 0.76 and 10.34 ± 1.3, respectively, at T₁ (p < 0.0001) and to the final values of 6.34 ± 0.62 and 11.0 ± 8.9, respectively, at T₂ (UCLA: T₂ versus T₁: p = 0.132; T₂ versus T₀: p < 0.0001; HAAS: T₂ versus T₁: p = 0.0027; T₂ versus T₀: p < 0.001). BMI ranged from a preoperative value of 27.97 ± 3.63 to a final value of 26.84 ± 3.11 (p < 0.0001). The only differences within the subgroups concerned patients with BMI ≥ 28, showing a superior HAAS at each follow-up (p < 0.05). A positive correlation was found between BMI and HAAS at T₀ and T₂ (p < 0.05).

Conclusions

This is the first study to evaluate the rate of the return to sports activities and change in BMI following hypoallergenic UKA. The majority of patients reduced their weight following UKA and improved their physical activity, showing outcomes that were comparable to the standard cobalt–chrome (CoCr) prostheses, regardless of gender, age, BMI and implant size.

Level of evidence

IV – Prospective Cohort Study.

Trial registration researchregistry5978—Research Registry www.researchregistry.com

Supplementary Information

The online version contains supplementary material available at 10.1186/s10195-021-00598-4.

Unicompartmental Knee Arthroplasty: Minimal Important Difference and Patient Acceptable Symptom State for the Forgotten Joint Score

Background and Objectives: Unicompartmental knee arthroplasty (UKA) is a valid alternative to total knee arthroplasties (TKAs) in selected cases. After surgery, patients' experience and satisfaction were traditionally evaluated by pre- and postsurgical scores and Patient-Reported Outcome Measures (PROMs). Otherwise, a statistically significant change does not necessarily correlate to a clinically meaningful improvement when measured using PROMs. To evaluate the real effect of a specific treatment and understand the difference between groups in a clinical trial, it is necessary to use a meaningful quantum of change on the score assessed. The minimal clinically important difference (MCID) and the Patient Acceptable Symptom State (PASS) can provide this meaningful change. This paper aimed to calculate the MCID and the PASS of the Forgotten Joint Score (FJS-12) after UKA. Materials and Methods: A total of 40 patients with a mean age 72.5 ± 6.4 years undergoing UKA were assessed preoperatively and six months postsurgery using the FJS-12 and the Oxford Knee Score (OKS). The baseline and 6-month postoperative scores were compared using the Wilcoxon signed ranks test. The correlation was calculated with Spearman's rho. Both distribution-based approaches and anchor approaches were used to estimate MCID for the FJS-12. The 75th percentile and the Receiver operating characteristic (ROC) curve methods were used to calculate the PASS of FJS-12. Results: MCID estimates for normalized FJS-12 for UKA ranged from 5.68 to 19.82. The threshold of the FJS-12 with ROC method was 72.92 (AUC = 0.76). The cut-off value computed with the 75th percentile approach was 92.71. Conclusions: The MCID and PASS represent valid tools to assess the real perception of clinical improvement in patients who underwent UKA. The MCID value of FJS-12 was 12.5 for patients who underwent UKA. The value of the PASS for the FJS-12 in patients who underwent UKA was 72.92.

[Effect of body mass index on short- and medium-term effectiveness of unicompartmental knee arthroplasty]

Objective

To investigate the effect of body mass index (BMI) on the short- and medium-term effectiveness of unicompartmental knee arthroplasty (UKA) in the treatment of anterior medial compartmental osteoarthritis of knee joint.

Methods

The clinical data of 55 patients (61 knees) with anterior medial compartmental osteoarthritis of knee joint treated with minimally invasive UKA between May 2014 and May 2019 were retrospectively analyzed. According to BMI, the patients were divided into 3 groups: normal body mass group [group A, BMI 18.50-24.99 kg/m ², 23 cases (25 knees)], overweight group [group B, BMI 25.00-29.99 kg/m ², 23 cases (25 knees)], obesity group [group C, BMI 30.00-39.99 kg/m ², 9 cases (11 knees)]. There was no significant difference in gender, age, sides, disease duration, and preoperative American Special Surgery Hospital (HSS) score, pain visual analogue scale (VAS) score, and knee range of motion (ROM) among 3 groups ( P>0.05). The operation time, intraoperative dominant blood loss, and the postoperative decreased amount of hemoglobin at 1 week were recorded and compared among 3 groups. The HSS score, VAS score, and ROM were used to evaluate the knee function and pain improvement.

Results

There was no significant difference in the operation time, the intraoperative dominant blood loss, and the postoperative decreased amount of hemoglobin at 1 week among 3 groups ( P>0.05). All the 55 patients were followed up 5-60 months, with an average of 24 months. No complication such as infection, fat embolism, or deep venous thrombosis of lower extremity occurred after operation. The anteroposterior and lateral X-ray films of the knee joint showed that no dislocation or loosening of the prosthesis occurred and the position of the prosthesis was good. At last follow-up, the HSS score, VAS score, and ROM of the 3 groups were significantly improved when compared with preoperative ones ( P<0.05); but there was no significant difference among 3 groups ( P>0.05).

Conclusion

For obese and overweight patients with anterior medial compartmental osteoarthritis of the knee joint, the use of minimally invasive UKA can achieve satisfactory short- and medium-term effectiveness, and the long-term effectiveness needs further follow-up.

Mid-term functional, clinical, and radiological outcomes with factors affecting revision of mobile-bearing medial unicompartmental knee arthroplasty

BACKGROUND

To evaluate and compare the clinical and radiological outcomes of patients subjected to medial unicompartmental knee arthroplasty (UKA).

METHODS

The study included 146 knees of 115 consecutive medial UKAs patients with a minimum five-year follow-up. Pre- and postoperative functional and clinical outcomes were measured using the Visual Analog Scale (VAS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Oxford Knee Score (OKS), American Knee Society Score (AKSS-O), knee range of motion (ROM), and Short-Form Health Survey (SF-36). The Kellgren-Lawrence osteoarthritis (OA) grading system was used for the evaluation of the OA status. The joint line convergence angle (JLCA) of the operated and contralateral knee, the tibiofemoral coronal angle (TFCA), and the tibial slope angle were used in the radiological evaluation.

RESULTS

The mean age of patients was 58.8 ± 7.0 years. The mean follow-up period was 7.41 ± 1.54 years. Good to excellent functional outcomes were obtained according to VAS, WOMAC, OKS, AKSS-O, and SF-36 scores. Insert dislocation was the main reason for revision surgery (nine patients, 90%). Preoperative body mass index (BMI), postoperative BMI, American Society of Anesthesiologists (ASA) Score, postoperative knee flexion contracture, mean increase in postoperative medial joint space (PMJS) height, and OA progression were found to affect the revision status.

CONCLUSIONS

Good to excellent functional, clinical, and radiological outcomes were obtained with medial UKA at a minimum follow-up of five years. Differences in preoperative and postoperative radiological parameters except an increase in PMJS height had no impact on revision status.

[Research progress in unicompartmental knee arthroplasty]

OBJECTIVE

To summarize the clinical application and research progress in unicompartmental knee arthroplasty (UKA).

METHODS

The literature related to UKA in recent years was reviewed and the emerging indications, implant options, comparisons between other surgical techniques, and recent advances were summarized.

RESULTS

Clinical studies show that UKA has many advantages, such as less trauma, faster recovery, and fewer postoperative complications. At present, the operative indication has been expanded. The body mass index more than 25 kg/m 2, less than 60 years old, patellofemoral arthritis, and anterior cruciate ligament dysfunction are no longer considered as contraindications. The prosthesis type in UKA should be selected according to the patient's condition. In recent years, the robot-assisted UKA can effectively improve the effectiveness, improve patient satisfaction, and reduce postoperative complications.

CONCLUSION

With the development of surgical techniques, designs of prosthesis, and the robotic technology, UKA would be further applicated. As more long-term data on UKA become available, it will further guide clinicians in counseling patients on whether UKA should be performed.

Inferior outcome of revision of unicompartmental knee arthroplasty to total knee arthroplasty compared with primary total knee arthroplasty: systematic review and meta-analysis

PURPOSE

The purpose of this study was to compare the revision of unicompartmental knee arthroplasty (UKA) to total knee arthroplasty (TKA) with primary TKA through a review of previously published studies. The hypothesis was that the revised UKA group would need additional operative procedures, including the use of stems and augments, resulting in poorer clinical outcomes than those of the primary TKA group.

METHODS

A literature search of online register databases was performed to identify clinical trials that compared revised UKA to TKA with primary TKA. An electronic literature search was performed using the Medline, Embase, Cochrane Library, Web of Science, and Scopus databases. No language or date restrictions were applied.

RESULTS

A total of 2034 articles were identified from a keyword search, of which 11 studies were determined as eligible. They were all retrospective comparative studies. The revised UKA to TKA group had longer operation times resulting from additional procedures such as bone grafting and use of stems and augments, higher reoperation rates, and worse postoperative clinical outcomes based on the Western Ontario and McMaster Universities Osteoarthritis Index and Oxford Knee Score than the primary TKA group, with the differences being statistically significant.

CONCLUSION

UKA should not be considered an alternative procedure to TKA.

LEVEL OF EVIDENCE

Therapeutic Level III.