Clinical results two years after total hip arthroplasty with a dual-mobility hemispherical cup

Introduction

Dislocation is a costly and feared complication of total hip arthroplasty (THA), reported in up to 7% of primary THA. [1], Jonker RC, Van Beers L, VanderWal BCH, et al. Les coupes à double mobilité peuvent-elles prévenir la luxation sans augmenter les taux de révision dans l'arthroplastie totale de la hanche primaire ? A systematic review. Orthop Traumatol Surg Res 2020;106(3):509. [2] Reina N, Pareek A, Krych AJ, Pagnano MW, Berry DJ, Abdel MP. Constructions à double mobilité dans l'arthroplastie totale de la hanche primaire et de révision : une revue systématique des études comparatives. J Arthroplasty 2019;34(3):594. . Over the past decade, dual-mobility (DM) cups have been demonstrated to be effective at reducing subluxations and dislocations, due to their greater jumping distance and higher ratio of head to neck diameter [3] Batailler C, Fary C, Verdier R, Aslanian T, Caton J, Lustig S. L'évolution des résultats et des indications de la cupule à double mobilité : une revue systématique. Int Orthop 2017;41(3):645. . Contemporary DM cups have been proven to effectively prevent intraprosthetic dislocation, and have shown low rates of complications and revision [3], Batailler C, Fary C, Verdier R, Aslanian T, Caton J, Lustig S. L'évolution des résultats et des indications de la cupule à double mobilité : une revue systématique. Int Orthop 2017;41(3):645. [4] DarrithB, CourtneyPM, DellaValleCJ. Résultats des composants à double mobilité dans l'arthroplastie totale de la hanche : une revue systématique de la littérature. Bone Joint J 2018;100-b(1):11. . Iliopsoas impingement remains a potential worry with DM cups, as they are more likely to overhang at the anterior margin of the acetabulum given that they are designed with a protruding cylindrical-spherical rim to increase the jumping distance [5] Vandenbussche E, Saffarini M, Deloge N, Moctezuma JL, Nogler M. Hemispheric cups do not reproduce acetabular rim morphology. Acta Orthop 2007;78(3):327. .

Since 2014, the authors have been using a new DM hemispherical cup that does not have a protruding cylindrical-spherical rim (figure 1) in order to reduce the risk of iliopsoas impingement without any need to change the conventional positioning of the cup perioperatively, like unipolar cups

The purpose of this study was to determine the dislocation, complication and revision rate as well as the clinical rating of this DM hemispherical cup after a minimum of two years of follow-up.

Materials and methods

The authors looked at a consecutive case series of 332 primary hip arthroplasties (323 patients), carried out over two consecutive years by three surgeons (L.S., G.E. and F.C.) using the same uncemented DM hemispherical cup (Symbol cup DM HA, Dedienne Sante, Mauguio, France) for all primary hip arthroplasties, with no specific inclusion or exclusion criteria applied (all ages, indications, activity levels, all types of spinal-pelvic alignment). The procedures were performed using the posterolateral approach, with the same technique applied for acetabular reaming and positioning of the cup in all 332 hips. The operative data are summarised in Table 1.

Demographic and preoperative morphological data

The cohort consisted of 147 men (147 hips) and 185 women (194 hips), aged 72.3 ± 9.8 years (range, 45 to 96) with a body mass index of 26.5 ± 4.5 (range, 17 to 50). The aetiologies are summarised in table 2.

All patients were contacted after a minimum of two years of follow-up for a clinical evaluation using the modified Harris Hip Score (mHHS) [6] Byrd JW, Jones KS. Analyse prospective de l'arthroscopie de la hanche avec un suivi de 2 ans. Arthroscopy 2000;16(6):578. and the Oxford Hip Score (OHS) [7] Delaunay C, Epinette JA, Dawson J, Murray D, Jolles BM. Adaptations interculturelles du score Oxford-12 HIP à la population francophone. Orthop Traumatol Surg Res 2009;95(2):89. . Their cases files were used to document the implant materials, model and diameter, and any postoperative complications or revisions. If any patients presented with pain at the clinical evaluation, more extensive imaging investigations were performed to look for fractures, implant overhang, infection, loosening, etc.

Statistical analysis

The Shapiro-Wilk test was used to evaluate whether the distribution was normal. Univariate and multivariate analyses were performed once the relevant variables had been determined (age at the time of operation, sex, body mass index, cup size, head diameter, neck length and stem type) in order to identify any associations with the mHHS and OHS ratings. The P value for statistical significance was considered to be < 0.05. The statistical analyses were carried out using R version 3.5.3 (R Foundation for Statistical Computing, Vienna, Austria).

Results

In our cohort of 323 patients (332 hips), there were six perioperative complications, none of which was caused by the cup: four partial femoral fractures (1%) treated with cerclage wiring and two fractured greater trochanters (0.5%, in patients aged between 81 and 85 years) treated with trochanteric plate fixation.

In addition, two patients (2 hips, 0.6%) required stem and cup revision due to persistent hip pain that was unrelated to the cup: one was due to an excessive overall mediolateral offset, and the other was due to stem loosening with suspected sepsis. Three patients (1%) needed stem-only revisions due to a traumatic periprosthetic femoral fracture of both hips and a leg length discrepancy exceeding 20 mm caused by the stem being progressively pushed into one hip.

There were ten postoperative complications (3%) that did not result in removal of the implant: three (0.9%) cases of impingement between the cup and psoas (treated by steroid injection), one (0.3%) deep surgical site infection successfully treated with irrigation and replacement of the moving parts (PE liner), and one (0.3%) leg length discrepancy exceeding 10 mm managed with a shoe-lift. Finally, there were two (0.6%) periprosthetic femoral fractures caused by a trauma, one (0.3%) case of traumatic fascia lata inflammation, one (0.3%) case of trochanteric bursitis and one (0.3%) oedema with blistering, all of which were treated conservatively. Thirteen patients (13 hips, 4%) had died and none were lost to follow-up. No dislocations were recorded during the follow-up phase.

Clinical results

For the final cohort of 305 living patients (314 hips) with their original cup and stem, assessed after 2.8 ± 0.5 years (range 2–5 years), the mHHS was 92 ± 12 (range 46–100), and the OHS was 57 ± 5 (range 34–60). The multivariate analyses showed that the mHHS and OHS values fell significantly with age, while only the mHHS increased with the acetabular cup diameter (tables 3 and 4).

Discussion

The popularity of DM cups has been growing recently because they deliver an acceptable range of motion while preventing instability [1], Jonker RC, Van Beers L, VanderWal BCH, et al. Les coupes à double mobilité peuvent-elles prévenir la luxation sans augmenter les taux de révision dans l'arthroplastie totale de la hanche primaire ? A systematic review. Orthop Traumatol Surg Res 2020;106(3):509. [2] Reina N, Pareek A, Krych AJ, Pagnano MW, Berry DJ, Abdel MP. Constructions à double mobilité dans l'arthroplastie totale de la hanche primaire et de révision : une revue systématique des études comparatives. J Arthroplasty 2019;34(3):594. . In view of the absence of dislocations and our satisfactory short-term clinical scores, this important cohort offers confirmation that the new DM hemispherical cup that we studied is effective in the prevention of dislocation, although longer term follow-up is still needed to check the longevity of the clinical results and stability of radiography [2], Reina N, Pareek A, Krych AJ, Pagnano MW, Berry DJ, Abdel MP. Constructions à double mobilité dans l'arthroplastie totale de la hanche primaire et de révision : une revue systématique des études comparatives. J Arthroplasty 2019;34(3):594. [4], DarrithB, CourtneyPM, DellaValleCJ. Résultats des composants à double mobilité dans l'arthroplastie totale de la hanche : une revue systématique de la littérature. Bone Joint J 2018;100-b(1):11. [10] Romagnoli M, Grassi A, Costa GG, Lazaro LE, Lo Presti M, Zaffagnini S. The efficacy of dual-mobility cup in preventing dislocation after total hip arthroplasty : a systematic review and meta-analysis of comparative studies. Int Orthop 2019;43(5):1071. .

This study suggests that DM hemispherical cups could be as effective in the prevention of dislocation as other contemporary DM cups with protruding cylindrical-spherical rims [1], Jonker RC, Van Beers L, VanderWal BCH, et al. Les coupes à double mobilité peuvent-elles prévenir la luxation sans augmenter les taux de révision dans l'arthroplastie totale de la hanche primaire ? A systematic review. Orthop Traumatol Surg Res 2020;106(3):509. [3], Batailler C, Fary C, Verdier R, Aslanian T, Caton J, Lustig S. L'évolution des résultats et des indications de la cupule à double mobilité : une revue systématique. Int Orthop 2017;41(3):645. [10] Romagnoli M, Grassi A, Costa GG, Lazaro LE, Lo Presti M, Zaffagnini S. The efficacy of dual-mobility cup in preventing dislocation after total hip arthroplasty : a systematic review and meta-analysis of comparative studies. Int Orthop 2019;43(5):1071. . In addition, the short-term data showing an absence of intraprosthetic instability where the cup meets the liner or where the liner meets the head indicates that 22 mm and 28 mm heads are compatible with this cup design. However, it remains unclear whether larger femoral heads are advantageous: while on the one hand they can reduce dislocation rates, on the other, they can cause increased wear of the liner [11], Leclercq S, Benoit JY, de Rosa JP, Tallier E, Leteurtre C, Girardin PH. Douille double mobilité Evora® chrome-cobalt : résultats à 10 ans de suivi minimum. Orthop Traumatol Surg Res 2013;99(8):923. [12] Bunn A, Colwell Jr CW, D'Lima DD. Effet du diamètre de la tête sur la luxation dynamique passive et active de la hanche. J Orthop Res 2014;32(11):1525. .

This study produced satisfactory clinical results for an uncemented THA using a new DM hemispherical acetabular cup without a protruding cylindrical-spherical rim, with a cumulative revision rate for the cup of 0.6% and an overall cumulative revision rate of 1.5%, after a mean follow-up period of 2.8 years. While the overall cumulative revision rate may seem high for such a short follow-up period, it should be noted that some of these were due to traumatic periprosthetic fractures and that the rate is within the range reported with other contemporary DM acetabular cups [4], DarrithB, CourtneyPM, DellaValleCJ. Résultats des composants à double mobilité dans l'arthroplastie totale de la hanche : une revue systématique de la littérature. Bone Joint J 2018;100-b(1):11. [8], Plummer DR, Haughom BD, Della Valle CJ. La double mobilité dans l'arthroplastie totale de la hanche. Orthop Clin North Am 2014;45(1):1. [9] Chouteau J, Rollier JC, Bonnin MP, et al. Absence d'instabilités et de luxations intra-prothétiques entre 7 et 11 ans après une PTH utilisant une cupule acétabulaire sans ciment à double mobilité de quatrième génération. J Exp Orthop 2020;7(1):51. .

For this case series, the means of the mHHS and OHS after 2 to 5 years were 92 and 57 points, respectively, which are favourable compared to the scores reported for contemporary DM cups [2] Reina N, Pareek A, Krych AJ, Pagnano MW, Berry DJ, Abdel MP. Constructions à double mobilité dans l'arthroplastie totale de la hanche primaire et de révision : une revue systématique des études comparatives. J Arthroplasty 2019;34(3):594. . Our multivariate regressions showed significant associations between age and the mHHS and OHS, which is to be expected since function declines in elderly patients.

In this study, a clinical diagnosis of iliopsoas impingement was given if a patient presented with anterior groin pain. Radiographs were then taken in these patients to exclude other possible causes of pain, and if no other cause of pain was found, CT scans were performed to quantify the overhang and anteversion of the cup. Psoas impingement caused by an excessive overhang and inadequate anteversion was identified in 3 hips (0.9%) even though DM hemispherical cups were used, probably due to insufficient anteversion of the cup or oversizing. Vandenbussche et al. [5] Vandenbussche E, Saffarini M, Deloge N, Moctezuma JL, Nogler M. Hemispheric cups do not reproduce acetabular rim morphology. Acta Orthop 2007;78(3):327. had in fact cautioned that implant overhang would be more likely to occur with DM cups in view of their more prominent rims. Nonetheless, the incidence of iliopsoas impingement in our case series is considerably lower than the rates seen in previous cases series (4.3%) [13] Ala Eddine T, Remy F, Chantelot C, Giraud F, Migaud H, Duquennoy A. Anterior iliopsoas impingement after total hip arthroplasty : diagnosis and conservative treatment in 9 cases. Rev Chir Orthop Reparatrice Appar Mot 2001;87(8):815. , and in other recent case series with unipolar cups (3.9%) [14] Ueno T, Kabata T, Kajino Y, Inoue D, Ohmori T, Tsuchiya H. Facteurs de risque et seuils de protrusion de la cupule pour le conflit iliopsoas symptomatique après arthroplastie totale de la hanche : une étude rétrospective cas-témoins. J Arthroplasty 2018;33(10):3288. .

The limitations of this study included its retrospective design and absence of radiographic evaluation. The minimum duration of follow-up of two years was insufficient for a robust survival analysis, but it was long enough to detect common early complications related to the cup, such as instability, dislocation or iliopsoas impingement. The main strength of this study was the sample size of 332 hips, which consisted of patients subject to hip instability, with a DM hemispherical cup. Although four types of stem were used, the same DM cup implant was used in all patients.

Conclusion

In view of the absence of dislocations and our satisfactory clinical scores, this important cohort offers confirmation that the new DM hemispherical cup that we studied is effective in the prevention of dislocation, although longer term follow-up is still needed to check the longevity of the clinical results and stability of radiography.