Cementless revision femoral stems application of press-fit principles and clinical outcomes.

BACKGROUND: Cementless femoral stems are currently used in revision total hip arthroplasty (THA) with the surgeon choosing between various fixation modes. The outcomes are good in the medium term; however, some failures have been attributed to technical errors during implantation. When the decision has been made to use a press-fit implant, the impact of the surgeon's technique on the functional outcomes have not been explored in-depth. This led us to carry out a retrospective study on a large population of total hip arthroplasty patients which aims were achieved press-fit to (1) determine the impact of the type of primary fixation (with and without press-fit) on the functional outcomes; (2) specify the effect of stem length on the functional scores when diaphyseal press-fit is achieved and (3) analyse the main reasons why a true press-fit effect was not achieved (three-point fixation). HYPOTHESIS: There is a relationship between the primary fixation method by press-fit of a revision femoral stem and the functional outcomes. PATIENTS AND METHODS: We performed a retrospective analysis of a continuous cohort of 244 THA revision cases with a mean follow-up of 6.1 ± 3.5 years (range, 2-18). The femoral area in which close contact was achieved (shared interface between the bone and implant) was used to define various types of press-fit fixation. The functional outcomes were determined using the Harris Hip Score (HHS) and the Merle d'AubignéPostel score (MAP score) out of 12 points (pain and walking items). RESULTS: The post-operative HHS averaged 90.83 ± 7.51 for proximal press-fit and 80.14 ± 14.93 with no press-fit (p = 0.01). The MAP averaged 10.83 ± 1.03 for proximal press-fit and 9.75 ± 2.09 with no press-fit (p = 0.09). The MAP score was worse for long diaphyseal press-fit than for short press-fit (p = 0.02). Use of a long stem with an endofemoral route or an overly small femoral window in patients with a curved femur is the main reason that three-point fixation occurred instead of press-fit. CONCLUSIONS: While press-fit is an effective concept, it is a demanding one that requires the surgeon to choose the correct surgical strategy for the patient's anatomy. A meticulous surgical technique is required to achieve proximal press-fit or at a minimum, short diaphyseal press-fit.

Global radiological score for femoral cementless revision stem.

PURPOSE: The purpose of this study was to evaluate the outcomes of total hip arthroplasty (THA) revision with cementless stems using a numeric global radiological score (GRxS) that summarizes two previously validated scores: secondary bone stock (SBS) and osseointegration-secondary stability (O-SS). METHOD: One hundred fifty cases of THA were evaluated at a mean follow-up of 6.5 ± 3.7 years. The GRxS combines the SBS, which evaluated cortical bone thickness, bone density and bone defects in each Gruen zone and the O-SS, which evaluated the location and extent of a single radiolucent line. To calculate the GRxS, the SBS and O-SS were each expressed on a 10-point scale and given equal weighing. The final result was a number out of 20. The GRxS was used to assign a radiological grade to each THA case: very good (20), good (18-15), average (13-12), or poor (≤ 10). The numerical mean (Nm) was calculated for each grade. The inter- and intra-observer reproducibility was evaluated. RESULTS: The inter-observer reproducibility was good (0.8) and the intra-observer reproducibility was very good (0.9). The GRxS was considered very good in 46 cases (Nm 20), good in 57 cases (Nm 16.6), average in 25 cases and poor in 22 cases. There was a significant relationship between the GRxS and the Harris Hip and Postel Merle d'Aubigné scores (p < 0.0001), and the initial bone stock (p = 0.0001). CONCLUSIONS: The GRxS is reliable and reproducible. This information can be used by surgeons to adapt the surgical technique to bone characteristics (especially during revision cases) and to compare the outcomes of different implant designs.

Assessment of fixation in cementless femoral revision of total hip arthroplasty: comparison of the Engh score versus radiolucent line measurement.

PURPOSE: To assess osseointegration and stability of a primary cementless femoral stem, many scoring systems have been developed, but none of them have taken into account only the radiolucent line. The purposes of this study were (1) to compare the results between the Engh score to assess osseointegration and stability of the cementless stem with results of a score called the O-SS score (osseointegration-secondary stability), which takes into account the radiolucent line, (2) to verify the relationship between these two scores and the functional results, and (3) to verify if there is a relationship between the O-SS score and secondary subsidence or a pedestal. METHODS: A clinical and radiological evaluation was performed in a group of 100 hip prosthesis revisions comparing the results obtained by Engh score and O-SS score for which reproducibility was analysed. RESULTS: Inter-observer reproducibility was estimated to be average at 0.5 and intra-observer reproducibility good at 0.7. The correlation with the Engh score was good at r = 0.59 (p < 0.0001). For the 80 cases assessed O-SS score as very good/good, Harris hip score was at 83.7 versus 78.25 for the 20 cases assessed as average/poor (p = 0.07). For the 73 cases with assessed Engh score as very good/good, this score was at 82.8 versus 82.14 for the 27 cases assessed as average/poor. No correlation between the O-SS score and secondary subsidence (p = 0.2) or pedestal (p = 0.2) was noticed. CONCLUSION: The evaluation of the clear radiolucent line alone, extent and location, is a sufficient condition to assess osseointegration and secondary stability of a cementless femoral stem.

Bone stock in revision femoral arthroplasty: a new evaluation.

PURPOSE: The purpose of this study was to finalize a method allowing a qualitative and numerical evaluation of the bone stock and to confirm its reproducibility, to verify the relationship between the secondary bone stock value and the functional results, and to determine the main factors influencing the value of the bone stock. METHODS: A clinical and radiological evaluation was performed in a group of 150 revisions of total hip replacements according to a new method taking into account cortical bone thickness, bone density and bone defects. RESULTS: Interobserver reproducibility was evaluated at an average of 0.6 and intra-observer reproducibility was considered good at 0.8. Between the initial bone stock and at the last follow-up, no significant difference was noticed. For secondary bone stock considered as "very good or good", the gain was +38.1 points versus +29.9 points for patients evaluated as "average or poor" (p < 0.0001). Between the initial bone stock assessment and at last follow-up, a significant relation was found in numerical values for the global type of primary fixation and in the presence of osteopenia (p < 0.0001). CONCLUSIONS: Deficient secondary bone stock can result in less favourable functional results. The numerical scores confirm the importance of strategic choices during surgery in order to manage bone stock preservation.

Stem and osteotomy length are critical for success of the transfemoral approach and cementless stem revision.

BACKGROUND: The transfemoral approach is an extensile surgical approach that is performed routinely to facilitate cement and implant removal and improve exposure for revision stem implantation. Previous studies have looked at clinical results of small patient groups. The factors associated with fixation failure of cementless revision stems when using this approach have not been examined. QUESTIONS/PURPOSES: We determined (1) the clinical results and (2) complications of the transfemoral approach and (3) factors associated with fixation failure of revision stems when using the transfemoral approach. PATIENTS AND METHODS: We retrospectively examined all our patients in whom femoral stem revision was performed through a transfemoral approach between December 1998 and April 2004 and for whom a minimal followup of 2 years was available. One hundred patients were available for this study. The mean (± SD) postoperative followup was 5 years (± 1.64 years). RESULTS: The average Harris hip score improved from 45.2 (± 14.02) preoperatively to 83.4 (± 11.86) at final followup. Complete radiographic bony consolidation of the osteotomy site was observed in 95% of patients. Dislocations occurred in 9% of patients. Four revision stem fixation failures were observed, all occurring in patients with primary three-point fixation. Three-point fixation was associated with short osteotomy flaps and long revision stems. CONCLUSIONS: The transfemoral approach is associated with a high rate of osteotomy flap bony healing and good clinical results. When using the transfemoral approach, a long osteotomy flap should be performed and the shortest possible revision stem should be implanted. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.