The data from the period of July 1, 2008 to July 31, 2018 were obtained from the CSMC database, which is a government-funded initiative that began in 2002. The registry records of 312 patients who had undergone a conversion from PFNA to CTHA (PCA) or to UTHA (PUA) during the study period were retrospectively analysed. The conversion procedure was carried out as stated by the manufacturers’ instructions at three medical institutions by 6 surgeons, who were all experienced in arthroplasty. The technical details and postoperative protocol have been reported in our prior study. The inclusion criteria were as follows: active elderly patients aged ≥ 60 years old; patients with a prior IFF (Type AO/OTA 31. A) treated with PFNA (a solid titanium nail, 200 -240 mm in length, 11-16 mm in diameter, 125° or 130° in collodiaphyseal angle, Smith & Nephew, Memphis, Tennessee), followed by CTHA (an Exeter Universal stem and an All-poly cup [Stryker, Mahwah, NJ]) or UTHA (an Taperloc stem [Biomet, Warsaw, Ind] and a polyethylene cup [HCC, Houston, Tex]); and patients with a failed fixation due to screw cut-out, mal-/non-union, or avascular necrosis. The main exclusion criteria included inadequate baseline data, hip dysplasia, active metabolic bone diseases, dyskinesia, lower extremity sensory disorders, metastatic diseases, severe medical diseases, dependence on alcohol or drug abuse, inability to follow instructions, vascular cognitive impairment, and an American Society of Anesthesiologists (ASA) score of IV or V. The ICD -10- Chinese Modification codes were applied to identify the relevant conditions mentioned in the exclusion criteria.
Based on our inclusion and exclusion criteria, 244 consecutive patients (244 hips) were identified from the registry with a mean follow-up period of 5 years (PCA: n = 120, mean age, 68.22±7.45 years; PUA: n = 124, mean age, 68.65±7.36 years), as illustrated in Figure 1. At the final follow-up, the mean follow-up duration was 64 months (range, 57 – 71 months) for the PCA group and 64 months (range, 58 - 71 months) for the PUA group. The patient-specific details and preoperative data were collected and are shown in Table 1.
Clinical and radiographic analysis
The clinical and radiographic evaluations were retrospectively reviewed by two authors (SM and BC) at 1, 3, 6, and 12 months postoperatively and yearly thereafter. The primary outcome measure was the HHS (range, 0 - 100), which was used to determine the functional level and evaluate pain. The secondary outcome measure was the rate of major orthopaedic complications, including prosthesis revision, loosening, periprosthetic fracture, dislocation, periprosthetic infection, intolerable hip pain, lower limb shortening, and thrombotic events. Radiographic analysis consisted of anteroposterior views of the hip and pelvis and a true lateral view of the hip.
The follow-up time was defined as the time interval between the date that CTHA or UTHA was performed and the date of the final follow-up. The definition of loosening of either the stem or the acetabulum on radiography was based on a previous description. Periprosthetic infection was determined according to the previously reported criteria. Stress shielding was determined by the classification of Engh et al. Osteolysis was evaluated by the criteria of McLaughlin et al. Heterotopic ossification was assessed per the Brooker classification system. Prosthesis revision was defined as removal of the CTHA or UTHA device for any reason. Between-group differences in the HHS or the major orthopaedic complications were compared using the nonparametric independent samples t-test or the chi-squared test, respectively. A significant difference was defined as a two-sided p value < 0.05. All statistical analyses were performed in SPSS 24.0 software (IBM, Armonk, NY, USA).