The Coronal Plane Alignment of the Knee (CPAK) classification has been developed to predict individual variations in inherent knee alignment. The impact of preoperative and postoperative CPAK classification phenotype on the postoperative clinical outcomes of total knee arthroplasty (TKA) remains elusive. This study aimed to examine the effect of postoperative CPAK classification phenotypes (I to IX), and their pre- to postoperative changes on patient-reported outcome measures (PROMs). A questionnaire was administered to 340 patients (422 knees) who underwent primary TKA for osteoarthritis (OA) between September 2013 and June 2019. A total of 231 patients (284 knees) responded. The Knee Society Score 2011 (KSS 2011), Knee injury and Osteoarthritis Outcome Score-12 (KOOS-12), and Forgotten Joint Score-12 (FJS-12) were used to assess clinical outcomes. Using preoperative and postoperative anteroposterior full-leg radiographs, the arithmetic hip-knee-ankle angle (aHKA) and joint line obliquity (JLO) were calculated and classified based on the CPAK classification. To investigate the impact on PROMs, multivariable regression analyses using stepwise selection were conducted, considering factors such as age at surgery, time since surgery, BMI, sex, implant use, postoperative aHKA classification, JLO classification, and changes in aHKA and JLO classifications from preoperative to postoperative.Aims
Methods
Although periacetabular osteotomies are widely used for the treatment of symptomatic acetabular dysplasia, the surgical outcomes after long term follow-up are still limited. Thus, we assessed hip survival and patient-reported outcomes (PROMs) at 20 years after the transposition osteotomy of acetabulum (TOA). Among 260 hips in 238 patients treated with TOA, 172 hips in 160 patients were evaluated at average 20.8 years, excluding patients who died or lost to follow-up. Kaplan-Meier analysis was used to assess survivorship with an end-point of THA. PROMs were evaluated using the VAS satisfaction, VAS pain, Oxford hip score (OHS), and Forgotten joint score (FJS). The thresholds of favorable outcomes of FJS and OHS were obtained using the receiver-operating characteristic curve with VAS satisfaction ≥ 50 and VAS pain < 20 as anchors. Thirty-three hips (19.2%) underwent THA at average 13.3 years after TOA. Kaplan-Meier analysis revealed hip survival rate at 20 years was 79.7%. Multivariate analysis showed the preoperative Tönnis grade significantly influenced hip survival. Survival rates with Tönnis grade 0, grade 1, and grade 2 were 93.3%, 86.7%, and 54.8% at 20 years, respectively. More than 60% of the patients showed favorable PROMs (VAS satisfaction ≥ 50, VAS pain < 20, OHS ≥ 42, FJS ≥ 51). Advanced Tönnis grade at the latest follow-up and higher BMI were significantly associated with unfavorable OHS, but not with other PROMs. This study demonstrated the durability of TOA for hips with Tönnis grade 0–1 and favorable satisfaction in majority of the patients at 20 years after surgery. Current presence of advanced osteoarthritis is associated with the lower hip function (OHS), but not necessarily associated with subjective pain and satisfaction. Higher BMI also showed a negative impact on postoperative function.
