How critical is body mass index, and who decides?

Gender, BMI, and Age-Related Variations in Lower Limb Alignment Parameters and CPAK Phenotypes in Chinese Patients with Knee Osteoarthritis

OBJECTIVES

Research on the distribution of and the variation in coronal plane alignment of the knee (CPAK) in the Chinese osteoarthritis population is limited. We aimed to establish the CPAK classification based on the characteristics of lower limb alignment in the Chinese osteoarthritis population. We also investigated variations in lower limb alignment parameters and CPAK phenotypes based on gender, body mass index (BMI), and age.

METHODS

A retrospective study was conducted on a total of 944 knees diagnosed with osteoarthritis in 479 patients from January 2017 to December 2023. A scatterplot was used to describe the distribution of the CPAK classification, and the differences in lower limb alignment parameters and the CPAK classification were compared across genders (male, female), ages (middle-aged/<65 years, elderly/≥65 years), and BMI categories (normal/<25 kg/m2, overweight and obese/≥25 kg/m2) using the chi-squared test or Fisher's exact test.

RESULTS

The average arithmetic hip-knee-ankle angle and joint line obliquity (JLO) were -3.03° ± 5.69° and 174.45° ± 4.29°, respectively. There was a higher prevalence of constitutional varus alignment in males and the overweight or obese group, while constitutional valgus alignment was more common in females and the normal BMI group (p < 0.05). Additionally, females had a greater apex distal JLO than males (p < 0.05). There were no statistically significant differences in lower limb alignment parameters among different age groups (p > 0.05). Although there were variations in alignment parameters across different genders and BMI categories in the knee osteoarthritis population, the predominant CPAK classifications were type I (38.03%), followed by type II (20.02%) and type IV (17.06%).

CONCLUSION

The most common CPAK types were I, II, and IV, and they were not influenced by gender, BMI, or age, indicating that the CPAK classification can reliably reflect constitutional alignment. A better understanding of native alignment variability can aid in providing patient-specific recommendations when considering orthopedic alignment strategies.

Increased fat depth is not associated with increased risk of surgical complications following total hip arthroplasty

AIMS

Previous research has demonstrated increased early complication rates following total hip arthroplasty (THA) in obese patients, as defined by body mass index (BMI). Subcutaneous fat depth (FD) has been shown to be an independent risk factor for wound infection in cervical and lumbar spine surgery, as well as after abdominal laparotomy. The aim of this study was to investigate whether increased peritrochanteric FD was associated with an increased risk of complications in the first year following THA.

METHODS

We analyzed prospectively collected data on a consecutive series of 1,220 primary THAs from June 2013 until May 2018. The vertical soft tissue depth from the most prominent part of the greater trochanter to the skin was measured intraoperatively using a sterile ruler and recorded to the nearest millimetre. BMI was calculated at the patient's preoperative assessment. All surgical complications occuring within the initial 12 months of follow-up were identified.

RESULTS

Females had a significantly greater FD at the greater trochanter in comparison to males (median 3.0 cm (interquartile range (IQR) 2.3 to 4.0) vs 2.0 cm (IQR 1.7 to 3.0); p < 0.001) despite equivalent BMI between sexes (male median BMI 30.0 kg/m² (IQR 27.0 to 33.0); female median 29.0 kg/m² (IQR 25.0 to 33.0)). FD showed a weak correlation with BMI (R² 0.41 males and R² 0.43 females). Patients with the greatest FD (upper quartile) were at no greater risk of complications compared with patients with the lowest FD (lower quartile); 7/311 (2.3%) vs 9/439 (2.1%); p = 0.820 . Conversely, patients with the highest BMI (≥ 40 kg/m²) had a significantly increased risk of complications compared with patients with lower BMI (< 40 kg/m²); 5/60 (8.3% vs 18/1,160 (1.6%), odds ratio (OR) 5.77 (95% confidence interval (CI) 2.1 to 16.1; p = 0.001)).

CONCLUSION

We found no relationship between peritrochanteric FD and the risk of surgical complications following primary THA. Cite this article: Bone Joint J 2020;102-B(9):1146-1150.

Predicting patient reported outcome in total knee arthroplasty using body mass index and limb measurements

BACKGROUND

Body mass index (BMI) has not been shown to correlate with Patient Reported Outcome Measures (PROMs) following total knee arthroplasty (TKA). We investigated the relationship between weight, BMI, limb morphology, and Oxford Knee Score (OKS). Furthermore, the utility of a novel radiological measurement, the Knee Mass Index (KMI), was investigated.

METHODS

Data including weight, BMI, gender, preoperative and 12 month OKS were collected from an arthroplasty database that contained 268 patients who underwent TKA. Measurements of soft tissue and bone width were made from the preoperative radiograph and 'KMI' was calculated. Pearson correlation and multivariate regression analyses were used to assess the relationship between OKS and the above variables.

RESULTS

The novel measurement, KMI, was not a predictor of the OKS. The BMI was predictive of initial OKS (Odds Ratio (OR) -0.26 p < 0.001), 12 month OKS (OR -0.39 p < 0.001) and change in OKS (OR -0.39 p < 0.001). The initial OKS was predictive of 12 month OKS (OR 0.32 p < 0.001) and change in OKS (OR -0.68 p < 0.001).

CONCLUSIONS

The novel KMI metric was not useful in predicting function. Both the post-operative OKS and change in OKS are predicted by BMI and pre-operative OKS. This is one of the first studies to show a relationship between BMI and OKS.