We report the follow-up of a cohort of 86 patients who underwent total hip replacement (THR) with custom-made stem prosthesis. Fixation mode, cemented (group 1) or uncemented (group 2) is based on the bone quality. Aspects of physical health and changes in mental health are documented using 3 patient-administered questionnaires, pre-operatively and 6 weeks, 3, 6 and 12 months post-operatively.

Harris Hip Score (HHS), Hip disability and osteoarthritis outcome score (HOOS) and SF-36, multi-purpose, short-form health survey were used.

Globally HHS increases significantly (p< 0.01). In group 1 up to 3 months post-operatively and in group 2 up to 1 year. (p < 0.05). In group 2 HHS is significantly higher 6 months and 1 year postoperatively (p< 0.05). No significant differences in HOOS subscores between subjects of group 1 and 2 for subsequent time points were found. The scores related to Pain and Symptoms increased significantly 6 weeks after THR (p< 0.01). Sports and recreation scores increased significantly up to 3 months after THR (p< 0.01). Activities of daily living, and Quality of Life (QoL) improved up to 6 months after surgery (p< 0.01).

No significant difference between the 2 groups in QoL was observed. The physical component summary increased up to 3 months after surgery (p< 0.01). The mental component summary did not change significantly after THR.

The difference noted in HHS between group 1 and 2 may be due to the selection of the fixation technique which is often directly related to the patient’s age. The results of the HOOS score confirm the findings of the HHS. Not all patients responded to the questions relative to recreation and sport of the HOOS score. QoL is an important indicator for success as perceived by the patient. In this study a rapid improvement of QoL is observed (3 months) and there is little change at 6 and 12 months.

Radiostereometric analysis (RSA) is a technique that can be used to measure in-vivo micro-motion of the components of hip arthroplasty.

86 patients received a titanium custom-made prosthesis. The average age was 64 year (20y –84y). During the study 30 patients out of 86 received a cementless femoral stem. The choice of stem fixation is determined by the quality of the bone. In all cases a 36 mm cobalt chromium head is used. Spherical tantalum markers, chosen because of the proven biocompatibility, were inserted into stable locations in the femoral bone during surgery using a specialized insertion tool, according to the protocol. Evaluation was done 1, 6, 12, 24, 52 weeks after surgery.

Overall subsidence follows a parallel pattern for the cemented and uncemented prosthesis that is slightly stronger in for the uncemented prosthesis. Over the 6 months evaluation period the prosthesis migrates towards the lateral side with 0.25 mm in both groups. An anteroversion of 0.5° to 1° is noted at 6 months follow-up. The varus valgus movement of the prosthesis is similar for both groups at 6 months. At 6 weeks a slight valgus flexion is noted, this is reversed at 3 months. At this point in time the effect is more pronounced in the group with a cemented prosthesis.

Micro motion is difficult to assess on plain radiography. In this study more subsidence is noted in the uncemented prosthesis compared to the cemented. The degree of rotation of the stem measured in our study is comparable with those reported by others. In our primary THR we observe a bi-modal micromotion except for the subsidence the initial movement up till 6 weeks is reversed at 3 months follow-up and at 6 months the prosthesis seems stabilized, though longer follow-up is required to confirm stabilization.

We present the results of a prospective longitudinal follow-up study of Dual X-ray Absorptiometry (DXA) measurements of the evolution of bone mineral density (BMD) of acetabulum and femur in 86 patients who underwent total hip arthroplasty (THA). A standard uncemented cup and intra-operatively manufactured stem prosthesis was used in all patients. Stem fixation was determided by the bone quality Thirthy patients received cementless and 56 patients received cemented stem prosthesis. Post-operative DXA scans were obtained in peri-prosthetic bone at 10 days, 6 weeks, 3, 6 and 12 months after THA. Peri-prosthetic BMD values in the proximal femur were obtained in the 7 Gruen zones. In the acetabulum a 4 region of interest model (ROI) was used.

Bimodal significant femoral BMD changes are found in all Gruen zones except for zone 1 of the cemented group where an immediate recovery is observed. The recovery mostly starts after 6 months of follow-up and the highest remodelling is found in the calcar region reaching even values of −16% at 6 months but no statistical significance was observed between the two groups. Significant linear losses (p< 0.0001) are observed in the pelvis region independent of type of fixation except the opposite change (p< 0.01) in the inferior region observing an immediate recovery in the uncemented group.

We compared the impact of a cemented stem with a non cemented stem on the bone remodelling of the cup and found that there was a correlation between the type of fixation and the mode of remodelling at the acetabular level. This suggest that a parameter such as the flexibility my have an influence on the bone remodelling at the acetabulum level. The pattern of bone remodelling observed on the different Gruen zones reflects the local load transfer to peri-prosthetic bone.