Psoas tendinopathy is a potential cause of groin pain after primary total hip arthroplasty (THA). The direct anterior approach (DAA) is becoming increasingly popular as the standard approach for primary THA due to being a muscle preserving technique. It is unclear what the prevalence is for the development of psoas-related pain after DAA THA, how this can influence patient reported outcome, and which risk factors can be identified.

This retrospective case control study of prospectively recorded data evaluated 1784 patients who underwent 2087 primary DAA THA procedures between January 2017 and September 2019. Psoas tendinopathy was defined as (1) persistence of groin pain after DAA THA and was triggered by active hip flexion, (2) exclusion of other causes such as dislocation, infection, implant loosening or (occult) fractures, and (3) a positive response to an image-guided injection with xylocaine and steroid into the psoas tendon sheath. Complication-, re-operation rates, and patient-reported outcome measures (PROMs) were measured.

Forty-three patients (45 hips; 2.2%) were diagnosed with psoas tendinopathy according to the above-described criteria. The mean age of patients who developed psoas tendinopathy was 50.8±11.7 years, which was significantly lower than the mean age of patients without psoas pain (62.4±12.7y; p<0.001). Patients with primary hip osteoarthritis were significantly less likely to develop psoas tendinopathy (14/1207; 1.2%) in comparison to patients with secondary hip osteoarthritis to dysplasia (18/501; 3.6%) (p<0.001) or FAI (12/305; 3.9%) (p<0.001). Patients with psoas tendinopathy had significantly lower PROM scores at 6 weeks and 1 year follow-up.

Psoas tendinopathy was present in 2.2% after DAA THA. Younger age and secondary osteoarthritis due to dysplasia or FAI were risk factors for the development of psoas tendinopathy. Post-operatively, patients with psoas tendinopathy often also presented with low back pain and lateral trochanteric pain. Psoas tendinopathy had an important influence on the evolution of PROM scores.

The 3D interplay between femoral component placement on contact stresses and range of motion of hip resurfacing was investigated with a hip model. Pre- and post-operative contours of the bone geometry and the gluteus medius were obtained from grey-value CT-segmentations. The joint contact forces and stresses were simulated for variations in component placement during a normal gait. The effect of component placement on range of motion was determined with a collision model. The contact forces were not increased with optimal component placement due to the compensatory effect of the medialisation of the center of rotation. However, the total range of motion decreased by 33%. Accumulative displacements of the femoral and acetabular center of rotation could increase the contact stresses between 5–24%. Inclining and anteverting the socket further increased the contact stresses between 6–11%. Increased socket inclination and anteversion in combination with shortening of the neck were associated with extremely high contact stresses. The effect of femoral offset restoration on range of motion was significantly higher than the effect of socket positioning. In conclusion, displacement of the femoral center of rotation in the lateral direction is at least as important for failure of hip resurfacings as socket malpositioning.

Summary sentence

The bowing of the femur defines a curvature plane to which the proximal and distal femoral anatomic landmarks have a predictable interrelationship. This plane can be a helpful adjunct for computer navigation to define the pre-operative, non-diseased anatomy of the femur and more particularly the rotational alignment of the femoral component in total knee arthroplasty (TKA).

We report the outcome at a minimum of 10 years follow-up for 80 polished tapered stems performed in 53 patients less than 35-years-old with a high risk profile for aseptic loosening. Forty-six prosthesis were inserted for inflammatory hip arthritis and 34 for avascular necrosis. The mean age at surgery was 28 years in the inflammatory arthritis (17–35) and 27 years in the avascular necrosis (15–35) patients. At a mean follow-up of 14.5 years in the inflammatory arthritis group and 14 years in the avascular necrosis group respectively, survivorship of the 80 stems with revision of the femoral component for any reason as an endpoint was 100 % (95 % CI). Re-operation was because of failure of four metal-backed cups, 3 all polyethylene cups and one cementless cup. None of the stems were radiographically loose. All but two femoral components subsided within the cement mantle to a mean of 1.2 mm (0 tot 2.5) at final follow-up. Periarticular osteolysis was noted in 4 femurs in zone 7. This finding was associated with polyethylene wear and was only seen in those hips that needed revision for a metal backed cup loosening. Our findings show that the polished tapered stem has excellent medium-term results when implanted in young patients with high risk factors for aseptic loosening.

The Exeter stem is a polished cemented stem that has been associated with an excellent survivorship. However, this wedge shaped stem has also been associated with a relative higher risk for a peri-periprosthetic fracture due to the wedge-shaped configuration that can lead to a Vancouver type B2 fracture when the stem is being driven downwards inside the femoral canal by a traumatic blast. Traditionally, these fractures should be treated with a revision stem because the stem has become loosened in the fractured cement mantle. We present a case series of 5 cases where our treatment algorithm was to first let the non-displaced fracture to consolidate by 6 weeks of limited weight bearing as tolerated in order to conduct a second stage in-cement revision. This would simplify the revision procedure dramatically. However, all patients are currently pain free and do not require revision surgery although they are being monitored very closely.

We conclude that non-displaced Vancouver type B2 fractures can be approached by a 2 stage treatment algorithm where the initial step is to let the fracture consolidate with limited weight bearing.