Is reverse hybrid hip replacement the solution?

Advancement in total hip implant: a comprehensive review of mechanics and performance parameters across diverse novelties

The UK's National Joint Registry (NJR) and the American Joint Replacement Registry (AJRR) of 2022 revealed that total hip replacement (THR) is the most common orthopaedic joint procedure. The NJR also noted that 10-20% of hip implants require revision within 1 to 10 years. Most of these revisions are a result of aseptic loosening, dislocation, implant wear, implant fracture, and joint incompatibility, which are all caused by implant geometry disparity. The primary purpose of this review article is to analyze and evaluate the mechanics and performance factors of advancement in hip implants with novel geometries. The existing hip implants can be categorized based on two parts: the hip stem and the joint of the implant. Insufficient stress distribution from implants to the femur can cause stress shielding, bone loss, excessive micromotion, and ultimately, implant aseptic loosening due to inflammation. Researchers are designing hip implants with a porous lattice and functionally graded material (FGM) stems, femur resurfacing, short-stem, and collared stems, all aimed at achieving uniform stress distribution and promoting adequate bone remodeling. Designing hip implants with a porous lattice FGM structure requires maintaining stiffness, strength, isotropy, and bone development potential. Mechanical stability is still an issue with hip implants, femur resurfacing, collared stems, and short stems. Hip implants are being developed with a variety of joint geometries to decrease wear, improve an angular range of motion, and strengthen mechanical stability at the joint interface. Dual mobility and reverse femoral head-liner hip implants reduce the hip joint's dislocation limits. In addition, researchers reveal that femoral headliner joints with unidirectional motion have a lower wear rate than traditional ball-and-socket joints. Based on research findings and gaps, a hypothesis is formulated by the authors proposing a hip implant with a collared stem and porous lattice FGM structure to address stress shielding and micromotion issues. A hypothesis is also formulated by the authors suggesting that the utilization of a spiral or gear-shaped thread with a matched contact point at the tapered joint of a hip implant could be a viable option for reducing wear and enhancing stability. The literature analysis underscores substantial research opportunities in developing a hip implant joint that addresses both dislocation and increased wear rates. Finally, this review explores potential solutions to existing obstacles in developing a better hip implant system.

Primary Complex Total Hip Arthroplasty in Neglected Anterior Hip Dislocation With Comminuted Pertrochanteric Femur Fracture

Neglected anterior hip dislocation combined with comminuted pertrochanteric ipsilateral fracture of the femur is rare, with few reports in the literature. The present report describes the case of a 7-month-old neglected anterior hip dislocation with a pertrochanteric femoral fracture in a 45-year-old male patient. The patient was treated with total hip arthroplasty with proximal femoral reconstruction. The 2-year follow-up showed good clinical and radiological outcomes with a painless and mobile hip joint. The Harris-Hip score improved from 10 (preoperatively) to 89 (postoperatively) after 2 years. The patient was satisfied with the intervention and showed minimal lurch with ambulation with no leg-length discrepancy. However, long-term results from periodic follow-up are warranted.

Do Postoperative Results Differ in a Randomized Trial Between a Direct Anterior and a Direct Lateral Approach in THA?

BACKGROUND

The direct lateral approach to THA provides good exposure and is associated with a low risk of dislocations, but can result in damage to the abductor muscles. The direct anterior approach does not incise muscle, and so recovery after surgery may be faster, but it has been associated with complications (including fractures and nerve injuries), and it involves a learning curve for surgeons who are unfamiliar with it. Few randomized trials have compared these approaches with respect to objective endpoints as well as validated outcome scores.

QUESTIONS/PURPOSES

The purpose of this study was to compare the direct anterior approach with the direct lateral approach to THA with respect to (1) patient-reported and validated outcomes scores; (2) frequency and persistence of abductor weakness, as demonstrated by the Trendelenburg test; and (3) major complications such as infection, dislocation, reoperation, or neurovascular injury.

METHODS

We performed a randomized controlled trial recruiting patients from January 2012 to June 2013. One hundred sixty-four patients with end-stage osteoarthritis were included and randomized to either the direct anterior or direct lateral approach. Before surgery and at 3, 6, 12, and 24 months, a physiotherapist recorded the Harris hip score (HHS), 6-minute walk distance (6MWD), and performed the Trendelenburg test directly after the 6MWD. The patients completed the Oxford Hip Score (OHS) and the EQ-5D. The groups were not different at baseline with respect to demographic data and preoperative scores. Both groups received the same pre- and postoperative regimes. Assessors were blinded to the approach used. One hundred fifty-four patients (94%) completed the 2-year followup; five patients from each group were lost to followup.

RESULTS

There were few statistical differences and no clinically important differences in terms of validated or patient-reported outcomes scores (including the HHS, 6MWD, OHS, or EQ-5D) between the direct anterior and the lateral approach at any time point. A higher proportion of patients had a persistently positive Trendelenburg test 24 months after surgery in the lateral approach than the direct anterior approach (16% [12 of 75] versus 1% [one of 79]; odds ratio, 15; p = 0.001). Irrespective of approach, those with a positive Trendelenburg test had statistically and clinically important worse HHS, OHS, and EQ-5D scores than those with a negative Trendelenburg test. There were four major nerve injuries in the direct anterior group (three transient femoral nerve injuries, resolved by 3 months after surgery, and one tibial nerve injury with symptoms that persist 24 months after surgery) and none in the lateral approach.

CONCLUSIONS

Based on our findings, no case for superiority of one approach over the other can be made, except for the reduction in postoperative Trendelenburg test-positive patients using the direct anterior approach compared with when using the direct lateral approach. Irrespective of approach, patients with a positive Trendelenburg test had clinically worse scores than those with a negative test, indicating the importance of ensuring good abductor function when performing THA. The direct anterior approach was associated with nerve injuries that were not seen in the group treated with the lateral approach.

LEVEL OF EVIDENCE

Level I, therapeutic study.

Reverse hybrid total hip arthroplasty

Aims

This study aimed to evaluate implant survival of reverse hybrid total hip arthroplasty (THA) at medium-term follow-up.

Patients and Methods

A consecutive series of 1082 THAs in 982 patients with mean follow-up of 7.9 years (5 to 11.3) is presented. Mean age was 69.2 years (21 to 94). Of these, 194 (17.9%) were in patients under 60 years, 663 (61.3%) in female patients and 348 (32.2%) performed by a trainee. Head size was 28 mm in 953 hips (88.1%) or 32 mm in 129 hips (11.9%). Survival analysis was performed and subgroups compared using log rank tests.

Results

Ten-year survival (122 hips at risk) was 97.2% (95% confidence interval (CI) 95.77 to 98.11) for all-cause revision. There was no difference in survival by age (p = 0.50), gender (p = 0.78), head size (p = 0.63) or surgeon grade (p = 0.36). No acetabular components underwent revision for aseptic loosening in the entire series. Four (0.4%) aseptic stem failures occurred early at a mean of 2.5 years (0.6 to 4.8) and were associated with age under 60 years (p = 0.015). There was no difference in survival by gender (p = 0.12), head size (p = 0.43) or surgeon grade (p = 0.77) for stem revision.

Conclusion

This is the largest reported study into reverse hybrid THA and it confirms successful outcomes, irrespective of age, gender, head size and surgeon grade. Cite this article: Bone Joint J 2018;100-B:1010-17.

The Corail stem as a reverse hybrid - survivorship and x-ray analysis at 10 years

BACKGROUND

The use of a cemented cup together with an uncemented stem in total hip arthroplasty (THA) has become popular in Norway and Sweden during the last decade. The results of this prosthetic concept, reverse hybrid THA have been sparsely described.We report our experience of reverse hybrid THA, using the Elite plus polyethylene cemented cup together with the Corail fully hydroxyapatite-coated uncemented stem and a 28-mm alumina ceramic head.

PATIENTS AND METHODS

132 consecutive reverse hybrid hip arthroplasties were performed from January 2000 to December 2003 in 126 patients with a mean age of 54.3 years (28-65). All patients were routinely reviewed at 3 months, 1, 5, 7 and 10 years postoperatively. At each follow-up patients were seen either by a consultant orthopaedic surgeon or a senior trainee. Anteroposterior pelvic and lateral x-rays of the hip were taken at each visit. To estimate the survival of the THAs we used the Kaplan-Meier method with 95% confidence interval (CI). Logistic regression analysis was performed to determine which factors affected the presence of radiolucency around the femoral stem.

RESULTS

The mean follow-up was 11.1 years (9.0-14.2). 1 patient was lost to follow-up, and 7 patients were deceased at the time of 10-year follow up. At 10 years 7 patients have had further surgery. 5 for infection, 1 periprosthetic femoral fracture and 1 heterotopic bone formation. All stems were classified as well fixed. 2 cups were defined as loose at 10 years. 1 patient is scheduled for revision the other refused revision. The clinical outcome and radiological findings were assessed in 123 hips. The mean Harris Hip Score was 94 (35-100) at 10 years and the mean WOMAC score was 89 (30.2-100).

CONCLUSIONS

We report good results with respect to clinical outcome and survival of the reverse hybrid concept in patients younger than 65. A successful outcome depends on meticulous preoperative planning, use of modern cementing techniques in the acetabulum and experience in implanting an uncemented stem.

Reverse hybrid total hip arthroplasty

Background and purpose - The use of a cemented cup together with an uncemented stem in total hip arthroplasty (THA) has become popular in Norway and Sweden during the last decade. The results of this prosthetic concept, reverse hybrid THA, have been sparsely described. The Nordic Arthroplasty Register Association (NARA) has already published 2 papers describing results of reverse hybrid THAs in different age groups. Based on data collected over 2 additional years, we wanted to perform in depth analyses of not only the reverse hybrid concept but also of the different cup/stem combinations used. Patients and methods - From the NARA, we extracted data on reverse hybrid THAs from January 1, 2000 until December 31, 2013. 38,415 such hips were studied and compared with cemented THAs. The Kaplan-Meier method and Cox regression analyses were used to estimate the prosthesis survival and the relative risk of revision. The main endpoint was revision for any reason. We also performed specific analyses regarding the different reasons for revision and analyses regarding the cup/stem combinations used in more than 500 cases. Results - We found a higher rate of revision for reverse hybrids than for cemented THAs, with an adjusted relative risk of revision (RR) of 1.4 (95% CI: 1.3-1.5). At 10 years, the survival rate was 94% (CI: 94-95) for cemented THAs and 92% (95% CI: 92-93) for reverse hybrids. The results for the reverse hybrid THAs were inferior to those for cemented THAs in patients aged 55 years or more (RR =1.1, CI: 1.0-1.3; p < 0.05). We found a higher rate of early revision due to periprosthetic femoral fracture for reverse hybrids than for cemented THAs in patients aged 55 years or more (RR =3.1, CI: 2.2-4.5; p < 0.001). Interpretation - Reverse hybrid THAs had a slightly higher rate of revision than cemented THAs in patients aged 55 or more. The difference in survival was mainly caused by a higher incidence of early revision due to periprosthetic femoral fracture in the reversed hybrid THAs.

Implant Survival After Minimally Invasive Anterior or Anterolateral Vs. Conventional Posterior or Direct Lateral Approach: An Analysis of 21,860 Total Hip Arthroplasties from the Norwegian Arthroplasty Register (2008 to 2013)

BACKGROUND

Since 2008, there has been an increase in the use of minimally invasive surgery (MIS) through an anterior or anterolateral approach for total hip arthroplasty (THA) in Norway. We compared the MIS approaches with the conventional posterior and direct lateral approaches in terms of revision rates and risk of revision.

METHODS

On the basis of data in the Norwegian Arthroplasty Register, 21,860 THAs with an uncemented stem, performed between 2008 and 2013, were identified and included in the cohort. Of these THAs, 2,017 were done through an MIS anterior approach; 2,087, through an MIS anterolateral approach; 5,961, through a posterior approach; and 11,795, through a direct lateral approach. Follow-up ended on December 31, 2015. Two and 5-year survival rates were calculated using Kaplan-Meier survival analysis. Relative risk (RR) was calculated using Cox regression analysis, with adjustment for age, sex, primary diagnosis, American Society of Anesthesiologists (ASA) grade, femoral head size, cup fixation, type of articulation, and duration of surgery and using 6 revision end points based on cause: any cause, infection, dislocation, femoral fracture, aseptic loosening, and other/unknown cause. The median duration of follow-up was 4.3 years.

RESULTS

There were no significant differences among the surgical approaches with regard to the 2 and 5-year survival rates or RR of revision due to any cause. The RR of revision due to infection was 0.53 (95% confidence interval [CI] = 0.36 to 0.80, p = 0.002) for the MIS anterior and anterolateral approaches and 0.57 (95% CI = 0.40 to 0.80, p = 0.001) for the posterior approach compared with the direct lateral approach. The RR of revision due to dislocation was 2.1 (95% CI = 1.5 to 3.1, p < 0.001) for the posterior approach compared with the direct lateral approach but no significant difference in risk was found when the MIS anterior and anterolateral approaches were compared with the direct lateral approach (RR = 0.71, 95% CI = 0.40 to 1.3, p = 0.25).

CONCLUSIONS

The revision rates and risk of revision associated with the MIS anterior and anterolateral approaches were not increased compared with those of the conventional posterior and direct lateral approaches.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Comparison of markers for muscle damage, inflammation, and pain using minimally invasive direct anterior versus direct lateral approach in total hip arthroplasty: A prospective, randomized, controlled trial

It is proposed that the use of biochemical markers for muscle damage and inflammation provides an objective measure on invasiveness in total hip arthroplasty. We analyzed levels of creatine kinase and C-reactive protein (CRP) after total hip arthroplasty in patients randomized to minimally invasive direct anterior approach or direct lateral approach, also recording consumption of pain medication and levels of pain postoperatively. Eighty-three patients were operated by the use of anterior approach and eighty using lateral. Creatine kinase and CRP levels were measured preoperatively, creatine kinase directly after surgery, and both creatine kinase and CRP on postoperative day 1 through 4. The use of pain medication and levels of pain were recorded. Creatine kinase were higher in the anterior group compared to the lateral group, reaching statistical significance directly postoperative and on day 4. Levels of CRP did not differ, reaching a maximum of mean 52 mg/L on day 3. The use of pain medication was higher in the lateral group on the day of surgery (p = 0.011), and pain levels were higher on all days in the lateral group (p < 0.007). In conclusion, the use of minimally invasive anterior approach caused less pain, but higher postoperative levels of CK, than the use of direct lateral approach.

Association between fixation technique and revision risk in total hip arthroplasty patients younger than 55 years of age. Results from the Nordic Arthroplasty Register Association

OBJECTIVES

To evaluate implant survival following primary total hip replacement (THR) in younger patients. To describe the diversity in use of cup-stem implant combinations.

DESIGN

29,558 primary THRs osteoarthritis (OA) patients younger than 55 years of age performed from 1995 through 2011 were identified using the Nordic Arthroplasty Registry Association database. We estimated adjusted relative risk (aRR) of revision with 95% confidence interval (CI) using Cox regression.

RESULTS

In general, no difference was observed between uncemented and cemented implants in terms of risk of any revision. Hybrid implants were associated with higher risk of any revision (aRR = 1.3, CI: 1.1-1.5). Uncemented implants led to a reduced risk of revision due to aseptic loosening (aRR = 0.5, CI: 0.5-0.6), whereas the risk was similar for hybrid and cemented implants. Compared with cemented implants, both uncemented and hybrid implants led to elevated risk of revision due to other causes, as well as elevated risk of revision due to any reason within 2 years. 183 different uncemented cup-stem implant combinations were registered in Denmark, of these, 172 were used in less than 100 operations which is similar to Norway, Sweden and Finland.

CONCLUSIONS

Uncemented implants perform better in relation to long-term risk of aseptic loosening, whereas both uncemented and hybrid rather than cemented implants in patients younger than 55 years had more short-term revisions because problems due to dislocation, periprosthetic fracture and infection has not yet been completely solved. The vast majority of cup-stem combinations were used in very few operations.

Countrywise results of total hip replacement. An analysis of 438,733 hips based on the Nordic Arthroplasty Register Association database

BACKGROUND AND PURPOSE

An earlier Nordic Arthroplasty Register Association (NARA) report on 280,201 total hip replacements (THRs) based on data from 1995-2006, from Sweden, Norway, and Denmark, was published in 2009. The present study assessed THR survival according to country, based on the NARA database with the Finnish data included.

MATERIAL AND METHODS

438,733 THRs performed during the period 1995-2011 in Sweden, Denmark, Norway, and Finland were included. Kaplan-Meier survival analysis was used to calculate survival probabilities with 95% confidence interval (CI). Cox multiple regression, with adjustment for age, sex, and diagnosis, was used to analyze implant survival with revision for any reason as endpoint.

RESULTS

The 15-year survival, with any revision as an endpoint, for all THRs was 86% (CI: 85.7-86.9) in Denmark, 88% (CI: 87.6-88.3) in Sweden, 87% (CI: 86.4-87.4) in Norway, and 84% (CI: 82.9-84.1) in Finland. Revision risk for all THRs was less in Sweden than in the 3 other countries during the first 5 years. However, revision risk for uncemented THR was less in Denmark than in Sweden during the sixth (HR = 0.53, CI: 0.34-0.82), seventh (HR = 0.60, CI: 0.37-0.97), and ninth (HR = 0.59, CI: 0.36-0.98) year of follow-up.

INTERPRETATION

The differences in THR survival rates were considerable, with inferior results in Finland. Brand-level comparison of THRs in Nordic countries will be required.

Reverse hybrid and cemented hip replacement compared using radiostereometry and dual-energy X-ray absorptiometry: 43 hips followed for 2 years in a prospective trial

BACKGROUND AND PURPOSE

Total hip replacement (THR) with a reverse hybrid (RH), a combination of a cemented polyethylene cup and a cementless femoral stem, has been increasingly used in Scandinavia. In a randomized trial, we compared an RH THR with a proximal hydroxyapatite- (HA-) coated stem to a conventional cemented THR. Both groups received the same polyethylene cup.

PATIENTS AND METHODS

51 patients (52 hips) were included. Radiostereometry (RSA) and dual-energy X-ray absorptiometry (DEXA) were performed postoperatively and after 6, 12, and 24 months. 42 patients (43 hips) were followed for 2 years.

RESULTS

Mean cup rotation around the x-axis was 0.13° for the cemented group and -0.24° for the RH group (p = 0.03). Cup migration in the other axes, and stem migration and wear were similar between the 2 study groups. Bone remodeling around the cup was also similar between the groups. Bone loss in Gruen zone 1 was 18% for the cementless stems, as compared to an increase of 1.4% for the cemented ones (p < 0.001). Bone loss was similar in the other Gruen zones. Harris hip score and Oxford hip score were similar pre- and postoperatively in the 2 groups.

INTERPRETATION

In the present study, RH THR with a cementless hydroxyapatite-coated stem and conventional cemented THR did not show any major differences regarding stem migration and bone loss after 2 years of follow-up.

Hip arthroplasty

Total hip arthroplasty is a cost-effective surgical procedure undertaken to relieve pain and restore function to the arthritic hip joint. More than 1 million arthroplasties are done every year worldwide, and this number is projected to double within the next two decades. Symptomatic osteoarthritis is the indication for surgery in more than 90% of patients, and its incidence is increasing because of an ageing population and the obesity epidemic. Excellent functional outcomes are reported; however, careful patient selection is needed to achieve best possible results. The present economic situation in many developed countries will place increased pressure on containment of costs. Future demand for hip arthroplasty, especially in patients younger than 65 years, emphasises the need for objective outcome measures and joint registries that can track lifetime implant survivorship. New generations of bearing surfaces such as metal-on-metal, ceramic-on-ceramic, and metal-on-ceramic, and techniques such as resurfacing arthroplasty have the potential to improve outcomes and survivorship, but findings from prospective trials are needed to show efficacy. With the recall of some metal-on-metal bearings, new bearing surfaces have to be monitored carefully before they can be assumed to be better than traditional bearings.