The journey to preventing dislocation after total hip arthroplasty

Dislocation following total hip arthroplasty (THA) is a well-known and potentially devastating complication. Clinicians have used many strategies in attempts to prevent dislocation since the introduction of THA. While the importance of postoperative care cannot be ignored, particular emphasis has been placed on preoperative planning in the prevention of dislocation. The strategies have progressed from more traditional approaches, including modular implants, the size of the femoral head, and augmentation of the offset, to newer concepts, including patient-specific component positioning combined with computer navigation, robotics, and the use of dual-mobility implants. As clinicians continue to pursue improved outcomes and reduced complications, these concepts will lay the foundation for future innovation in THA and ultimately improved outcomes. Cite this article: Bone Joint J 2022;104-B(1):8–11.

Femoral Stem Fracture in Hip Revision Arthroplasty: A Systematic Literature Review of the Real-World Evidence

Background Total hip arthroplasty (THA) presents as an excellent treatment for the osteoarthritic hip, demonstrating good survival rates. However, aseptic loosening and infection are the main causes of operative revision. The methods used in revision surgery are non-modular or modular THA implants. In addition to the abovementioned revision reasons for THA, this treatment could be associated with the possibility of femoral stem fracture, especially in the modular system. The topic of material failure has been focused on in the public media. The question arises as to how such media reports correlate with the published literature. The observed mentioned number of cases concerning a femoral stem fracture vary between one single case and up to 18.5% within a clinical study, thus presenting an inhomogeneous data situation with a large span. The specific aim of this systematic review is to establish facts and clarify the number of unforeseen events of a femoral stem fracture based on peer review articles and registry data. This clarification is important to us, as these media reports have led to uncertainty among patients. Methods A systematic review was performed in accordance with the PRISMA statement. Peer review articles in English and German, presenting original articles, meta-analyses, or case reports, were searched from the turn of the millennium up to December 2019. Only articles that reported a femoral stem component fracture, with content of clinical data as well as register data, were included. Relevant papers published after the defined research time frame were taken into account within the discussion. Results In total, 218 fractures of a femoral stem (141 primary and 77 revision THA) component could be identified within the selected literature. Most cases of a femoral stem fracture occurred in the modular THA implants compared to the non-modular stems. Regarding revision THA, in summary, 77 implants, presenting 23 non-modular and 54 modular implants, failed by means of femoral stem fracture. A review of 11 National Joint Registries shows a revision rate between 0.04 and 0.05% in only 2 registers according to the specific subject of a femoral stem fracture. For the remaining 9 registers, however, detailed information is lacking and only nonspecific information such as a generic “implant failure” or “other reason” (which can cover a multitude of causes) is supplied. Conclusion A femoral stem fracture presents a devastating complication for the patient, the surgeon as well as for the manufacturer of the implant. Modular THA implants play an increasingly valuable role concerning restoration of individual anatomy in modern THA revision surgery, especially within complex cases. Regarding revision procedures, data suggests a lower risk of femoral stem fracture for modular implants compared to primary procedures, while the risk of fracture for non-modular implants seems to increase during revision. Ultimately, it cannot be proven whether this is actually applicable, since the absolute number of implanted prosthesis systems is not known. Various implant-, patient-, and surgeon-related factors may lead to these reported femoral stem fractures. However, this systematic review suggests that this is, in general, a rare complication.

Metal-on-metal total hip arthroplasty: does increasing modularity affect clinical outcome?

Background: Modularity of metal-on-metal (MoM) implants has come under scrutiny due to concerns regarding additional sources of metal debris. This study is a retrieval analysis of implants from the same manufacturer with the same MoM bearing surface. The difference between the implants was presence or absence of modular junctions. Methods: This is a retrospective study of 31 retrieved implants from 31 patients who received a Conserve Wright Medical MoM hip prosthesis. The 31 implants consisted of 16 resurfacings and 15 implants with modular junctions; 4 conventional THAs and 11 modular-neck THAs. Results: 43% of pre-revision MRI scans performed on resurfacing implants and 91% performed on the modular implants illustrated evidence of an adverse local tissue reaction. There was no difference in pre-revision blood metal ion levels or bearing surface wear between the resurfacings and modular implants. The neck-head tapers of the modular group showed low levels of material loss. However, the neck-stem tapers showed increased severity of corrosion and material loss Conclusions: The modular implants had an increased incidence of adverse local tissue reaction. This could be related to the presence of modular junctions, particular the neck-stem junction which showed increased susceptibly to corrosion

Comparison of two different on-shelf femoral stems for Crowe type IV developmental dysplasia of the hip

Objective This study was performed to evaluate the proximal anatomical compatibility of stems for treatment of Crowe IV developmental dysplasia of the hip (DDH) using a previously developed three-dimensional comparison technique. Methods Patients with Crowe IV DDH who underwent computed tomography were retrospectively analyzed. The femoral medullary canals were three-dimensionally reconstructed, and models of cementless modular (S-ROM; DePuy Synthes) and conical (Wagner Cone; Zimmer Biomet) implants were used for virtual implantation. The negative point percentages (NPPs) were applied to verify fitting. The average distance (deviation) and the root mean square of the distance (RMSd) were used to quantify geometric compatibilities. Results Four (16.7%) and 12 (50.0%) femoral medullary canals could not be fitted properly with either the modular or conical implant. The NPPs in the distal comparison region were significantly greater in the conical than modular group. The deviation was significantly smaller in the modular than conical group. The RMSd was also significantly smaller in the modular than conical group. Conclusions Compared with conical implants, modular implants might be more effectively used in patients with Crowe type IV DDH. However, some Crowe IV DDH femurs with severe deformity cannot be fitted with either of these two on-shelf implants.

Failure of Three Cementless Modular Total Hip Arthroplasty Prostheses: A Retrieval Analysis

The reasons leading to the in vivo failure of three titanium alloy modular implants in cementless total hip arthroplasty were investigated. The implantation period ranged from 18 months to over three years. Two were fractured in vivo and the other was retrieved secondary to aseptic loosening after 18 months in service. Macroscopic examination showed close topographical similarities between the two fractured implants. Dark elliptical striations on the fractured site indicated the occurrence of low cycle fatigue. Light Microscopy and Scanning Electron Microscopy confirmed the presence of fretting, pitting, plastic deformation, and stress-induced corrosion cracking. In two of the three implants, EDS confirmed metal ion traces in the tissue around the implant. However, nothing unusual was found in the third unfractured implant. Taper performance is influenced by metallurgy, the load carried and the effect of the local microenvironment. Methods to reduce the impact of these factors may reduce the incidence of taper related failure.