Femoral stem migration after direct lateral and direct anterior total hip arthroplasty: a prospective cohort study.

BACKGROUND: The direct lateral (DL) approach to total hip arthroplasty is more commonly used than the newer direct anterior (DA) approach. Both approaches use collared or collarless femoral stems. We sought to assess implant stability of stem designs implanted with the DL approach and compare outcomes from this cohort with those of a previously reported cohort of patients who underwent arthroplasty with a DA approach. We also sought to determine if early recovery influences differences in migration. METHODS: Patients underwent total hip arthroplasty using the DL or the DA approach and were randomized to receive either a collared or collarless, cementless femoral stem. On the day of surgery and at 6 follow-up visits through to 1 year, patients underwent supine radiostereometric imaging to track implant migration. At follow-up visits, patients performed an instrumented walking test to assess their functional ability and logged an average daily step count to assess their activity levels. We assessed whether patient function and activity were correlated with migration. RESULTS: Stem design did not have a significant effect on migration for the DL group (p = 0.894). Compared with the DA group, the DL group migrated significantly less for both collared (p = 0.031) and collarless (p = 0.002) stems. Migration was not correlated with function or activity at any time point (p > 0.05). CONCLUSION: Most implant migration occurred from the day of surgery to 2 weeks after the operation and stabilized thereafter, suggesting adequate fixation and a low risk for aseptic loosening in both patient groups.

Fully hydroxyapatite-coated collared femoral stems in direct anterior versus direct lateral hip arthroplastyFully hydroxyapatite-coated collared femoral stems in direct anterior versus direct lateral hip arthroplasty.

Background: Total hip arthroplasty (THA) via the direct anterior approach has increased in popularity in the last decade, with research supporting enhanced early recovery; however, some investigators have reported increased early revision rates in direct anterior THA. We examined outcomes from a single institution's experience with a fully hydroxyapatite-coated collared femoral stem implanted via the anterior or the lateral approach. Methods: Patients who had received fully hydroxyapatite-coated collared femoral stems as part of THA surgery performed by 1 of 3 surgeons between January 2012 and September 2017 were identified from our institutional database. We examined revision rates for the 2 approaches and compared them between the 2 groups. We also analyzed outcomes on plain film radiographs obtained immediately postoperatively and at 1 and 2 years. Results: A total of 695 patients received a fully hydroxyapatite-coated collared stem during the study period. Total hip arthroplasty was performed via the direct anterior approach in 281/778 hips (36.1%) and via the direct lateral approach in 497 (63.9%). Nineteen patients (2.5%) underwent subsequent revision surgery; there was no statistically significant difference in the revision rate between the anterior and lateral approaches (2.5% v. 2.4%, p = 0.95). The mean subsidence of the stem at 1 year was 1.68 mm (standard deviation 11.7 mm). No statistically significant differences were observed between the cohorts for any of the radiographic measurements at either follow-up time. Conclusion: We found no significant difference in revision rates between the direct anterior and direct lateral approach. Stem subsidence levels were in keeping with expected values, and no major changes in stem position occurred during the first postoperative year. Surgical approach did not appear to substantially affect biomechanical stem behaviour.

Contexte: L'arthroplastie totale de la hanche (ATH) par voie antérieure directe a gagné en popularité dans les 10 dernières années, la recherche ayant montré qu'elle favorisait un rétablissement rapide; certains chercheurs ont toutefois signalé qu'elle était associée à un taux accru d'opérations de révision précoces. Nous avons étudié les issues de l'installation d'une tige fémorale à collier entièrement recouverte d'hydroxyapatite par voie antérieure ou latérale dans un établissement. Méthodes: Nous avons interrogé la base de données de notre établissement pour y recenser les patients ayant subi, entre janvier 2012 et septembre 2017, une ATH au cours de laquelle 1 de 3 chirurgiens a installé une tige fémorale à collier entièrement recouverte d'hydroxyapatite. Nous avons ensuite examiné le taux d'opérations de révision pour les 2 approches étudiées, et avons comparé les issues des 2 groupes. Nous avons également analysé les clichés radiographiques pris immédiatement après l'intervention, de même de ceux pris aux suivis à 1 et à 2 ans. Résultats: Durant la période à l'étude, 695 patients se sont fait installer une tige fémorale à collier entièrement recouverte d'hydroxyapatite. Sur 778 hanches, 281 (36,1 %) avaient subi une ATH par voie antérieure directe, et 497 (63,9 %), une ATH par voie latérale directe. Dix-neuf patients (2,5 %) ont dû subséquemment subir une opération de révision; aucune différence statistiquement significative n'a été observée entre le groupe voie antérieure et le groupe voie latérale en ce qui a trait au taux de révision (2,5 % c. 2,4 %; p = 0,95). L'affaissement moyen de la tige au suivi à 1 an était de 1,68 mm (écart type 11,7 mm). Les mesures radiographiques des 2 groupes ne présentaient pas de différences statistiquement significatives, quel que soit le moment du suivi. Conclusion: Nous n'avons constaté aucune différence significative dans le taux de révision entre les 2 groupes. L'affaissement observé était dans les valeurs attendues, et la position de la tige n'avait pas changé de façon importante au cours de la première année. La voie chirurgicale utilisée ne semblait pas influencer considérablement le comportement biomécanique de la tige.

The effect of femoral stem collar on implant migration and clinical outcomes following direct anterior approach total hip arthroplasty.

AIMS: The direct anterior (DA) approach has been associated with rapid patient recovery after total hip arthroplasty (THA) but may be associated with more frequent femoral complications including implant loosening. The objective of this study was to determine whether the addition of a collar to the femoral stem affects implant migration, patient activity, and patient function following primary THA using the DA approach. METHODS: Patients were randomized to either a collared (n = 23) or collarless (n = 26) cementless femoral stem implanted using the DA approach. Canal fill ratio (CFR) was measured on the first postoperative radiographs. Patients underwent a supine radiostereometric analysis (RSA) exam postoperatively on the day of surgery and at two, four, six, 12, 26, and 52 weeks postoperatively. Patient-reported outcome measures (Western Ontario and McMaster Universities Osteoarthritis (WOMAC) Index, the 12-item Short Form Health Survey Mental and Physical Score, and University of California, Los Angeles (UCLA) Activity Score) were measured preoperatively and at each post-surgery clinic visit. Activity and function were also measured as the weekly average step count recorded by an activity tracker, and an instrumented timed up-and-go (TUG) test in clinic, respectively. RESULTS: Comparing the RSA between the day of surgery baseline exam to two weeks postoperatively, subsidence was significantly lower (mean difference 2.23 mm (SD 0.71), p = 0.023) with collared stems, though these patients had a greater CFR (p = 0.048). There was no difference (p = 0.426) in subsidence between stems from a two-week baseline through to one year postoperatively. There were no clinically relevant differences in PROMs; and there was no difference in the change in activity (p = 0.078) or the change in functional capacity (p = 0.664) between the collared stem group and the collarless stem group at any timepoint. CONCLUSION: Presence of a collar on the femoral stem resulted in reduced subsidence during the first two postoperative weeks following primary THA using the DA approach. However, the clinical implications are unclear, and larger studies examining patient activity and outcomes are required. Cite this article: Bone Joint J 2020;102-B(12):1654-1661.