Total hip arthroplasty (THA) is one of the most successful surgical procedures of modern times, however debate continues as to the optimal orientation of the acetabular component and how to reliably achieve this. We hypothesised that functional CT-based planning with patient specific instruments using the Corin Optimised Positioning System (OPS) would provide more accurate component alignment than the conventional freehand technique using 2D templating. A pragmatic single-centre, patient-assessor blinded, randomised control trial of patients undergoing THA was performed. 54 patients (age 18–70) were recruited to either OPS THA or conventional THA. All patients received a cementless acetabular component. Patients in both arms underwent pre- and post-operative CT scans, and four functional x-rays (standing and seated). Patients in the OPS group had a 3D surgical plan and bespoke guides made. Patients in the conventional group had a surgical plan based on 2D templating x-rays, and the pre-operative target acetabular orientation was recorded by the surgeon. The primary outcome measure was the difference between planned and achieved acetabular anteversion and was determined by post-operative CT scan performed at 6 weeks. Secondary outcome measures included Hip disability and Osteoarthritis Outcome Score (HOOS), Oxford Hip Score (OHS), EQ-5D and adverse events. In the OPS group, the achieved acetabular anteversion was within 10° of the plan in 96% of cases, compared with only 76% of cases in the conventional group. For acetabular inclination, the achieved position in the OPS group was within 10° of the plan in 96% of cases, compared with in only 84% of cases in the conventional group. These differences were not statistically significant. The clinical outcomes were comparable between the two groups. Large errors in acetabular orientation appear to be reduced when functional CT-based planning and patient-specific instruments are used compared to the freehand technique, but no statistically significant differences were seen in the difference between planned and achieved angles. Larger studies are needed to analyse this in more detail and to determine whether the reduced numbers of outliers lead to improved clinical outcomes.
Tissue sparing hip replacements have recently gained popularity, in an attempt to provide shorter hospital stay, faster recovery time and potentially to reduce morbidity and complications. Direct anterior approaches (DAA) have been shown to allow faster recovery, but also appear to be associated with a higher incidence of complications, especially during the learning curve. Mini-posterior approaches have the advantage of increased familiarity, however may not be maximally muscle sparing. Prospective and retrospective data was collected following a published protocol. This included patient demographic data, theatre time, units of blood transfused, length of stay, functional scores and radiological parameters. Rates of conversion to posterior approach and complications were also documented. The results of our first 100 cases completed are presented: Within this initial cohort, three patients suffered major complications: These included an anterior dislocation, which was successfully reduced with closed reduction under general anaesthetic, an early (day 6) periprosthetic fracture, which was successfully revised to a cemented prosthesis, and a case of stem subsidence. Our results also suggest a learning curve effect, limited to theatre time and blood loss. Complications were evenly distributed throughout the period of study and are of similar frequency to standard approaches. As the first European centre to adopt the SuperPATH approach, we have shown that the published results from America can be reproduced. In contrast to DAA, the learning curve is not associated with higher rates of femoral fracture and other complications. The fact that the approach is extensile, being the superior part of the posterior approach, allows for all of the advantages of muscle preservation with the safety of potential extension when necessary.
We used Laser Doppler flowmetry to measure the effect on the blood flow to the femoral head/neck junction of two surgical approaches during resurfacing arthroplasty. We studied 24 hips undergoing resurfacing arthroplasty for osteoarthritis. Of these, 12 had a posterior approach and 12 a trochanteric flip approach. A Laser probe was placed under radiological control in the superolateral part of the femoral head/neck junction. The Doppler flux was measured at stages of the operation and compared with the initial flux. In both groups the main fall in blood flow occurred during the initial exposure and capsulotomy of the hip joint. There was a greater reduction in blood flow with the posterior (40%) than with the trochanteric flip approach (11%).
