The effect of cemented acetabular component geometry on the risk of revision for instability or loosening

Aims To determine if primary cemented acetabular component geometry (long posterior wall (LPW), hooded, or offset reorientating) influences the risk of revision total hip arthroplasty (THA) for instability or loosening. Methods The National Joint Registry (NJR) dataset was analyzed for primary THAs performed between 2003 and 2017. A cohort of 224,874 cemented acetabular components were included. The effect of acetabular component geometry on the risk of revision for instability or for loosening was investigated using log-binomial regression adjusting for age, sex, American Society of Anesthesiologists grade, indication, side, institution type, operating surgeon grade, surgical approach, polyethylene crosslinking, and prosthetic head size. A competing risk survival analysis was performed with the competing risks being revision for other indications or death. Results The distribution of acetabular component geometries was: LPW 81.2%; hooded 18.7%; and offset reorientating 0.1%. There were 3,313 (1.5%) revision THAs performed, of which 815 (0.4%) were for instability and 838 (0.4%) were for loosening. Compared to the LPW group, the adjusted subhazard ratio of revision for instability in the hooded group was 2.31 (p < 0.001) and 4.12 (p = 0.047) in the offset reorientating group. Likewise, the subhazard ratio of revision for loosening was 2.65 (p < 0.001) in the hooded group and 13.61 (p < 0.001) in the offset reorientating group. A time-varying subhazard ratio of revision for instability (hooded vs LPW) was found, being greatest within the first three months. Conclusion This registry-based study confirms a significantly higher risk of revision after cemented THA for instability and for loosening when a hooded or offset reorientating acetabular component is used, compared to a LPW component. Further research is required to clarify if certain patients benefit from the use of hooded or offset reorientating components, but we recommend caution when using such components in routine clinical practice. Cite this article: Bone Joint J 2021;103-B(11):1669–1677.

The Symmetry and Predictive Factors in Two-Stage Bilateral Hip Replacement Procedures

Background: Approximately 10–25% of total hip replacement patients undergo a bilateral procedure. The purpose of this study was to compare selected parameters associated with the first and second hip arthroplasty in patients undergoing two-stage treatment due to bilateral hip osteoarthritis and establish the predictive factors for the second procedure. Methods: This study compared the data on bilateral total hip replacement surgeries conducted in the period between 2017 and 2021 (42 patients). The following parameters from the first and second procedure were compared: the prosthetic stem, head, and insert cup size; type of cup insert; duration of anesthesia; duration of hospitalization; and the number of complications. Results: The mean duration of hospital stay at the time of the first total hip arthroplasty was 5.83 days and 5.4 days during the second stay. The mean stem sizes used during the first and second total hip replacement procedures were 7.11 and 7.09, respectively. The mean sizes of endoprosthetic cups used at the first and second total hip replacement procedures were 52.64 and 53.04, respectively. There were no significant differences between the mean prosthetic head size at the first and second surgery. The cup type used during the first and second surgery showed no difference. The mean duration of anesthesia used during the first and second total hip replacement surgery was 108.09 min and 104.52 min, respectively. We recorded a mean of 0.07 complications per patient at the first surgery and 0.02 at the second surgery. Conclusions: Our study results showed symmetry duration of anesthesia, length of hospital stay, number of complications per patient, stem size, prosthetic head size, cup insert size, and cup insert type at the first and second surgery in patients with two-stage bilateral total hip arthroplasty. We observed a strong correlation between the stem sizes of the first and second hip endoprostheses. There was also a strong correlation between the cup sizes used during the first and second surgery.

Influence of Different Damage Patterns of the Stem Taper on Fixation and Fracture Strength of Ceramic Ball Heads for Total Hip Replacement

Background. Modularity finds frequent application in total hip replacement, allowing a preferable individual configuration and a simplified revision by retaining the femoral stem and replacing the prosthetic head. However, micromotions within the interface between the head and the stem taper can arise, resulting in the release of wear debris and corrosion products. The aim of our experimental study was to evaluate the influence of different taper damages on the fixation and fracture stability of ceramic femoral heads, after static and dynamic implant loading. Methods. Ceramic ball heads (36 mm diameter) and 12/14 stem tapers made of titanium with various mild damage patterns (intact, scratched, and truncated) were tested. The heads were assembled on the taper with a quasistatic load of 2 kN and separated into a static and a dynamic group afterwards. The dynamic group (n=18) was loaded over 1.5 million gait cycles in a hip wear simulator (ISO 14242-1). In contrast, the static group (n=18) was not mechanically loaded after assembly. To determine the taper stability, all heads of the dynamic and static groups were either pulled off (ASTM 2009) or turned off (ISO 7206-16). A head fracture test (ISO 7206-10) was also performed. Subsequent to the fixation stability tests, the taper surface was visually evaluated in terms of any signs of wear or corrosion after the dynamic loading. Results. In 10 of the 18 cases, discoloration of the taper was determined after the dynamic loading and subsequent cleaning, indicating the first signs of corrosion. Pull-off forces as well as turn-off moments were increased between 23% and 54% after the dynamic loading compared to the unloaded tapers. No significant influence of taper damage was determined in terms of taper fixation strength. However, the taper damage led to a decrease in fracture strength by approximately 20% (scratched) and 40% (truncated), respectively. Conclusion. The results suggest that careful handling and accurate manufacturing of the stem taper are crucial for the ceramic head fracture strength, even though a mild damage showed no significant influence on taper stability. Moreover, our data indicate that a further seating of the prosthetic head may occur during daily activities, when the resulting hip force increases the assembly load.

Clinical and radiological results with a 36-mm cobalt-chrome prosthetic head, cross-linked Durasul liners associated with Allofit cups: a more than 10-year follow-up period

Background: Highly cross-linked polyethylene is currently a common articulation surface used for total hip arthroplasty (THA). Aim: The aim of the present study is in vivo assessment of highly cross-linked Durasul polyethylene linear and volumetric wear when associated with a 36-mm prosthetic femoral head. Methods: We retrospectively reviewed clinical and radiographic data of 78 patients (81 hips) having primary THAs using Durasul liner combined with a 36-mm CoCr prosthetic head. All of them were followed for more than 10 years. Patient outcome was assessed with the Harris Hip Score (HHS) preoperatively and at last follow-up. 2-D prosthetic head penetration into polyethylene, 3D wear rates and cup migration were evaluated. Results: The preoperative and last follow-up HHS were 50.43 +/− 10.42 and 97.44 +/− 5.51 respectively. The annual penetration of the prosthetic head into Durasul® liner was 0.029 +/− 0.003 mm. The annual linear penetration and volumetric wear extrapolation rates using Charnley and Ilchmann formulas were 37.84% and 57.76% respectively of that seen with conventional polyethylene liner. At last follow-up, the total loss of material in Durasul represents only 0.15% of the initial polyethylene mass. We did not observe any significant cup migration in the study group. Conclusions: Results are promising, and we believe that these data authorise the continued use of highly cross-linked polyethylene liner associated with a 36-mm prosthetic head for total hip arthroplasties in older patients. More long-term follow-up studies are mandatory before we feel comfortable with the project of using cross-linked polyethylene in young and active patients instead of ceramic-on-ceramic bearings.

Aseptic Destruction of the Elbow Joint after Radial Head Replacement. Case Study

Radial head replacement should be a routine treatment in cases of non-reconstructable radial head fractures. With the growing number of radial head arthroplasties, we are going to see more complications related to this procedure. We describe a case of aseptic destruction of the elbow joint, probably related to the release of polyethylene particles from the prosthetic head. Removal of the implant and extensive synovectomy was performed, leading to an excellent clinical outcome with reduction of pain and increase in the range of motion. The clinical improvement was not accompanied by radiographic change.

Retentive Cup Arthroplasty in Selected Hip Fracture Patients—A Prospective Series With a Minimum 3-Year Follow-Up

Objective: To evaluate the efficacy of the use of retentive cup primary total hip replacement (THR) in high-dislocation risk subcapital fracture patients. Methods: During the years 2008 to 2012, 354 patients with displaced subcapital fracture were operated at our institute. The patients were selected to undergo primary constrained THR according to the following criteria: (1) a preinjury grade 4 or more on the Functional Independence Measure mobility item “5. Locomotion: walking/wheelchair” and grade 4 is defined as “4. Minimal assistance Requiring incidental hands-on help only” (patient performs >75% of the task) and (2) a disease leading to poor motor control. Exclusion criteria were normal muscular control and known infection of the involved joint. Results: Of the 354 patients, 87 fulfilled the inclusion criteria and underwent constrained total hip. Average age was 78 years with a female predominance (73%). Fifteen patients had prior hemiparesis, 19 had Parkinson disease, and 35 had generalized sarcopenia. Eighty-five patients had an uneventful recovery, with an average Hip Disability and Osteoarthritis Outcome Score (HOOS) of 76 ± 7 at 2 years. In 2 patients, the prostheses dislocated. In both cases, the dislocation was due to ring displacement and the inner head dislocated. One case was infected and the patient was treated by a Girdlestone procedure. In the other case, the prosthetic head was revised. The patient remained asymptomatic and at 4-year follow-up had an HOOS of 85. Discussion: It appears that constrained prosthesis is a suitable treatment for patients with poor muscular control having subcapital fractures. The functional results appear to be superior to those of bipolar arthroplasty and similar to the results of primary total hip arthroplasty while the dislocation risk is <3%. Conclusion: Semielective total hip arthroplasty using a retentive cup liner appears to offer good functional results with a low dislocation rate in patients with poor muscular control.

Acetabular cup liner and prosthetic head exchange to increase the head diameter for management of recurrent luxation of a prosthetic hip in two dogs

SummaryComponent malalignment and impingement are possible causes of recurrent luxation following total hip replacement in the dog. In the two cases presented in this report, luxation that was probably due to impingement was managed by exchanging the standard 17 mm prosthetic head for a 24 mm prosthetic head. This required removal of the original acetabular cup liner and placement of a new polyethylene liner that would accept the 24 mm head into the stable acetabular shell. In the first case, a 50 kg Malamute dog, recurrent luxation was initially managed by component alignment revision, iliofemoral suture, triple pelvic osteotomy and a novel lasso technique, without long-term success. After exchanging the head and cup liner, luxation did not recur over a 12-month period. In the second case, a 65 kg Newfoundland dog, impingement was suspected after a second luxation event. Luxation did not recur during the nine months after exchange of the head and cup liner. The larger prosthetic head used in these two cases increased the impingement-free range-of-motion of the joint and increased the translation distance required for luxation (jump distance).

Dual mobility canine total hip prosthesis: Implant characteristics and surgical procedure

SummaryProsthetic dislocation is one of the most common complications after canine hip replacement. The use of dual mobility acetabular components has been shown to reduce the rate of dislocation in first intent hip replacement in human patients who are at high risk for dislocation. In such implants, a mobile polyethylene liner articulates on one side with a metallic acetabular component and on the other side with a metallic prosthetic head. A dual mobility cemented acetabular component has been designed for use in dogs, and is available for use in association with a previously designed modular femoral component. This report describes the characteristics and the procedure for implantation of this implant combination.

Finite Element Modelling of Shock-Induced Damages on Ceramic Hip Prostheses

The aim of this work was to simulate the behaviour of hip prostheses under mechanical shocks. When hip joint is replaced by prosthesis, during the swing phase of the leg, a microseparation between the prosthetic head and the cup could occur. Two different sizes of femoral heads were studied: 28 and 32 mm diameter, made, respectively, in alumina and zirconia. The shock-induced stress was determined numerically using finite element analysis (FEA), Abaqus software. The influence of inclination, force, material, and microseparation was studied. In addition, an algorithm was developed from a probabilistic model, Todinov's approach, to predict lifetime of head and cup. Simulations showed maximum tensile stresses were reached on the cup's surfaces near to rim. The worst case was the cup-head mounted at 30°. All simulations and tests showed bulk zirconia had a greater resistance to shocks than bulk alumina. The probability of failure could be bigger than 0.9 when a porosity greater than 0.7% vol. is present in the material. Simulating results showed good agreement with experimental results. The tests and simulations are promising for predicting the lifetime of ceramic prostheses.