Numerous factors influence total hip arthroplasty (THA) stability including surgical approach and soft tissue tension, patient compliance, and component position. One long-held tenet regarding component position is that cup inclination and anteversion of 40° ± 10° and 15° ± 10°, respectively, represent a “safe zone” as defined by Lewinnek that minimizes dislocation after primary THA; however, it is clear that components positioned in this zone can and do dislocate.

We previously compared the 15-year survivorship of total knee arthroplasty (TKA) implants that were mechanically aligned (0° ± 3° relative to the mechanical axis) compared with those that were outside that range and considered outliers. The original publication included 398 TKAs (292 in the aligned group and 106 in the outlier group) performed from 1985 to 1990. At the time of follow-up in the previous study, 138 patients (155 TKAs) had died and 59 knees had been revised. Since that publication, 49 additional patients (87 knees) have died. At 20 years, 57 (19.5%) of the 292 knees in the mechanically aligned group had been revised compared with 16 (15.1%) of the 106 knees in the outlier group (p = 0.97). Postoperative alignment within 0° ± 3° of the mechanical axis did not provide a functional advantage at 1, 5, 10, 15, and/or 20 years postoperatively as demonstrated by the Knee Society scores being similar between the groups (p ≥ 0.2 at all intervals). At 20 years, we once again did not find that neutral mechanical alignment provided better implant survivorship than that found in the outlier group. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Background: For patients undergoing 2-stage exchange for the treatment of periprosthetic joint infection (PJI) following total knee arthroplasty, the long-term risk of reinfection and mechanical failure and long-term clinical outcomes are not well known. The purpose of our study was to determine the long-term clinical results of 2-stage exchange for PJI following total knee arthroplasty. Methods: We identified 245 knees that had undergone total knee arthroplasty and were subsequently treated with 2-stage exchange due to infection during the period of 1991 to 2006; the cohort had no prior treatment for PJI. Major, or 4 of 6 minor, Musculoskeletal Infection Society (MSIS) diagnostic criteria were fulfilled by 179 (73%) of the knees. The cumulative incidence of reinfection and of aseptic revision, accounting for the competing risk of death, were calculated. Risk factors for reinfection were evaluated using Cox proportional hazards regression. Knee Society Score (KSS) values were calculated. The mean age at spacer insertion was 68 years; 50% of the patients were female. The mean follow-up was 14 years (range, 2 to 25 years) following reimplantation. Results: The cumulative incidence of reinfection was 4% at 1 year, 14% at 5 years, 16% at 10 years, and 17% at 15 years. Factors that were predictive of reinfection included a body mass index of ≥30 kg/m² (hazard ratio [HR], 3.1; p < 0.01), previous revision surgery (HR, 2.8; p < 0.01), and a McPherson host grade of C (HR, 2.5; p = 0.04). The cumulative incidence of aseptic revision for loosening was 2% at 5 years, 5% at 10 years, and 7% at 15 years. Femoral (HR, 5.0; p = 0.04) and tibial (HR, 6.7; p < 0.01) bone-grafting at reimplantation were predictive of aseptic failure. The most common complications were wound-healing issues, requiring reoperation in 12 (5%) of the knees. The rate of death at 2 years following reimplantation was 11%. The mean KSS improved from 45 at PJI diagnosis to 76 at 10 years following reimplantation (p < 0.01). Conclusions: Long-term reinfection rates following 2-stage exchange for PJI after total knee arthroplasty were similar to those of shorter-term reports and were maintained out to 15 years. Mechanical failure rates were low if bone loss was addressed at the time of reimplantation. Improvements in clinical outcomes were maintained at long-term follow-up. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Background: Dislocation is one of the most common complications after revision THA. Dual-mobility constructs and large femoral heads (ie, 40 mm) are two contemporary, nonconstrained bearing options used in revision THA to minimize the risk of dislocation; however, it is not currently established if there is a clear benefit to using dual-mobility constructs over large femoral heads in the revision setting.Questions/purposes: We sought to determine if dual-mobility constructs would provide a reduction in dislocation, rerevision for dislocation, and reoperation or other complications as compared with large femoral heads in revision THA.Methods: From 2011 to 2014, a series of 355 THAs underwent revision for any reason and received either a dual-mobility construct (146 THAs) or a 40-mm large femoral head (209 THAs). Indications for either construct were based on surgeon judgment; however, there is a preference to use dual-mobility constructs in patients believed to be at higher risk of dislocation. In the dual-mobility group, 20 of 146 (14%) were excluded because of loss of followup before 2 years or because they had a dual-mobility shell cemented into a preexisting acetabular component. In the large head group, 33 of 209 (16%) were lost to followup before 2 years. Followup in the dual-mobility group was 3.3 ± 0.8 years and followup in the large head group was 3.9 ± 0.9 years. Primary endpoints included dislocation, rerevisions for dislocation, and reoperations, which were determined through our institution’s total joint registry and verified by individual patient chart review. Age and body mass index were not different with the numbers available between the groups, but there was a slight predominance of females in the dual-mobility group (52% [66 of 126] female) versus the 40-mm large head group (41% [72 of 176] female) (p = 0.05). Notably, 33% (41 of 126) of patients receiving the dual-mobility constructs had the index revision THA done for a diagnosis of recurrent dislocation versus 9% (17 of 176) in the 40-mm large head group. Mean effective head size in the dual-mobility group was 47 mm (range, 38–58 mm).Results: The subsequent frequency of dislocation in the dual-mobility construct group was less (3% [four of 126] dual-mobility versus 10% [17 of 176] in the 40-mm large head group; hazard ratio, 3.2 [1.1-9.4]; p = 0.03). Rerevision for dislocation in the dual-mobility construct group was less frequent (1% [one of 126] dual-mobility versus 6% [10 of 176] in the 40-mm large head group; hazard ratio, 7.1 [0.9-55.6]; p = 0.03). Reoperation for any cause in the dual-mobility construct group was less frequent (6% [eight of 126] dual-mobility versus 15% [27 of 176] in the 40-mm large head group; hazard ratio, 2.5 [1.1-5.5]; p = 0.02); there were no differences between the groups in terms of the overall percentage of complications in each group.Conclusions: When compared with patients treated with a 40-mm large femoral head, patients undergoing revision THA who received a dual-mobility construct had a lower risk of subsequent dislocation, rerevision for dislocation, and reoperation for any reason in the first several years postoperatively. Those findings were present despite selection bias in this study to use the dual-mobility construct in patients at the highest risk for subsequent dislocation. Given the lower risk of subsequent dislocation, rerevision, and reoperation with the dual-mobility construct, some surgeons may wish to consider whether the role of dual-mobility should be judiciously expanded in contemporary revision THA.Level of Evidence: Level III, therapeutic study.

Background: Total knee arthroplasty (TKA) with a rotating-hinge prosthesis is considered a salvage procedure. While excellent immediate stability is achieved, the historically high failure rate has tempered its use. The goal of this study was to determine clinical outcomes, radiographic results, and survivorship after TKA with contemporary rotating-hinge components. Methods: We identified 408 consecutive TKAs performed with rotating-hinge components for nononcologic indications from 2002 to 2012 at a single academic institution. Two hundred and sixty-four knees (65%) had rotating-hinge TKA components implanted for aseptic etiologies, while 144 knees (35%) were managed with the components in 2-stage reimplantation following infection. Rotating-hinge TKA implants were used for complex primary procedures in 74 knees (18%) and as a revision construct in 334 knees (82%). Clinical outcomes were assessed with the Knee Society scoring system, survivorship analyses, and cumulative incidence of revision. The mean age of the patients at the time of the index arthroplasty was 69 years, and the mean duration of follow-up was 4 years (range, 2 to 12 years). Results: At the most recent follow-up, the mean Knee Society knee score had increased from 51 points preoperatively to 81 points (p < 0.0001), and the mean Knee Society functional score had increased from 26 to 36 points (p < 0.0001). At a mean of 4 years, loosening of components was observed in 13 (3.7%) of 349 knees. At the most recent follow-up, 59 revision procedures and 25 reoperations had been performed. The cumulative incidence of any revision was 9.7% at 2 years and 22.5% at 10 years. The cumulative incidence of revision for aseptic loosening was 1.7% at 2 years and 4.5% at 10 years. Metaphyseal cones were used in 114 knees (28%). Survivorship analysis revealed a trend toward a lower risk of revision (hazard ratio [HR] = 0.69; 95% confidence interval [CI] = 0.39 to 1.22; p = 0.20) and reoperation (HR = 0.51; 95% CI = 0.22 to 1.19; p = 0.12) in patients with metaphyseal cones, despite their use in the most severe of bone defects. Conclusions: Contemporary rotating-hinge TKA implants had a low 10-year cumulative incidence of revision for aseptic loosening of 4.5%. Greater use of metaphyseal fixation has aided this improvement. Patients can expect substantial improvements in clinical outcomes with this revision strategy. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.