Prospective Study Deltamotion - DAA THA Study

Research protocol prospective study Deltamotion - DAA THA study

1. Introduction Very few gait analytical data are available concerning the Direct Anterior Approach (DAA) in total hip arthroplasty (THA). All the studies have focused on immediate post-operative recovery. These studies have in general some important shortcomings in order to accurately evaluate the biomechanics of the replaced hip joint. None of the published reports have reported on consecutive intervals of pre-op - 6w - 3m - 6m - 12m. This is of interest as we know that recovery with other approaches takes >1 year. It might be that the DAA approach leads to normal gait patterns at 3m or 6m and that these patterns do not differ from the normal pattern or at >1y post-op. None of the reports utilized out-of-plane movements such as coming down or up stairs or squads. Muscle strength of the abductors has not been tested. Utilizing trunk markers is frequently not done but it is important to evaluate the centre of mass position during gait. Very few studies utilize kinetic data, which are important in order to thoroughly evaluate the biomechanics and loading of the hip. And maybe most importantly, the biomechanical effect of the diameter of the articulating surface on gait parameters following the DAA has never been evaluated.

   One of the most important advantages of the DAA is the muscle sparing aspect and the presumption that the femoral anatomy and biomechanics can be more accurately and precisely restored. If the diameter of the articulating surface has then also been reconstructed to the almost anatomical diameter, we can assume that this should be the most optimal reconstruction of the hip joint currently available. This could lead to early return to normal gait, to optimal joint loading and a minimal amount of stress shielding of the femoral bone.

   The aim of this project is (1) to prospectively analyse the biomechanics of the hip joint of a THA with a Deltamotion articulating surface utilizing the Direct Anterior Approach and (2) to assess the femoral bone remodelling around the fully coated Corail stem over the first year post-operatively.

2. Materials and Methods Hypothesis: (1) The temporo-spatial parameters (velocity, cadence, step length, and stride length) and gait kinematic and kinetic data (external hip and knee muscle moments) are not significantly different between the study and control group at the evaluated time intervals indicating normal or near normal gait patterns in the early post-operative recovery phase. (2) Stress shielding of the bone around the femoral stem as measured with the DEXA scan can be predicted accurately with the FE analysis based on the collected data indicating the validity of the musculoskeletal models.

Estimated inclusion time: 1 July 2011 - 31 December 2011 Cohorts: 20 DAA subjects - 20 control subjects

Assessments:

• Time interval: pre-op - 3m - 6m - 12m

• Assessment of all subjects:

  • XR with magnification marker
  • Biodex force measurement in flexion and extension and mid flexion (with EMG if possible)

• Gait analysis with surface EMG and trunk markers:

  • Unipodal standing: 3 trials Right and 3 trials Left on FP
  • Level walking: 3 trials Right and 3 trials Left on FP
  • Chair rise: 3 trials, both legs on FP
  • Stair ascent: 3 trials Right and 3 trials Left on first FP
  • Stair descent: 3 trials Right and 3 trials Left on first FP
  • Squat: 3 trials, both legs on FP
  • Bipodal squat: 3 trials Right and 3 trials Left on FP
• Functional scores (HHS, UCLA, HOOS, SF-36)
• DEXA scan pre-op and at 12 months

• Assessment of final 5 subjects per group:

  • CT pre and post at 6w (pre: pelvis-knee and post: hip)
  • MRI pre and 1 y post
  • Accelerometer 1 week