Instruments to reduce the risk of tibial fracture following cementless unicompartmental knee replacement

A Comparison of the Periprosthetic Fracture Rate of Cemented and Cementless Mobile Bearing Unicompartmental Knee Arthroplasties: An Analysis of Data From the National Joint Registry for England, Wales, Northern Ireland, and the Isle of Man

BACKGROUND

Periprosthetic fractures are rare but serious complications of unicompartmental knee arthroplasty (UKA). Although cementless UKA has a lower risk of loosening than cemented, there are concerns that tibial fracture risk may be higher given the reliance on interference fit for primary stability. The risk of fracture and the effect of surgical fixation are currently unknown. We compared the periprosthetic fracture rate following cemented and cementless UKA surgery.

METHODS

A total of 14,122 medial mobile-bearing UKAs (7,061 cemented and 7,061 cementless) from the National Joint Registry and Hospital Episodes Statistics database were propensity score-matched. Cumulative fracture rates were calculated and Cox regressions were used to compare fixation groups.

RESULTS

The three-month periprosthetic fracture rates were similar (P = .80), being 0.10% in the cemented group and 0.11% in the cementless group. The fracture rates were highest during the first three months postoperatively, but then decreased and remained constant between one and 10 years after surgery. The one-year cumulative fracture rates were 0.2% (confidence interval [CI]: 0.1 to 0.3) for cemented and 0.2% (CI: 0.1 to 0.3) for cementless cases. The 10-year cumulative fracture rates were 0.8% (CI: 0.2 to 1.3) and 0.8% (CI: 0.3 to 1.3), respectively. The hazard ratio during the whole study period was 1.06 (CI: 0.64 to 1.77; P = .79).

CONCLUSIONS

The periprosthetic fracture rate following mobile bearing UKA surgery is low, being about 1% at 10 years. There were no significant differences in fracture rates between cemented and cementless implants after matching. We surmise that surgeons are aware of the higher theoretical risk of early fracture with cementless components and take care with tibial preparation.

LEVELS OF EVIDENCE

III.

Periprosthetic tibial fracture as a complication of unicompartmental knee arthroplasty: Current insights

Periprosthetic fracture following knee arthroplasty is a rare but devastating complication associated with significant morbidity. With unicompartmental knee arthroplasty being performed far less frequently than total knee arthroplasty, periprosthetic fracture following unicompartmental knee arthroplasty presents a particular challenge to orthopaedic surgeons, due to clinical unfamiliarity and sparsity of literature. An up-to-date review of the epidemiology, risk factors, and management strategies for PPF after UKA is presented.

A Comparison of the Periprosthetic Fracture Rate of Cemented and Cementless Total Knee Arthroplasties: An Analysis of Data From the National Joint Registry

BACKGROUND

Periprosthetic fractures are serious complications of knee arthroplasty often requiring complex surgery. There is concern of increased periprosthetic fracture risk with cementless components given the reliance on interference fit for primary stability. It is unknown how the periprosthetic fracture risk compares between cemented and cementless total knee arthroplasties (TKAs).

METHODS

A total of 22,477 cemented and 22,477 cementless TKAs from the National Joint Registry and Hospital Episodes Statistics database were propensity score matched on patient and surgical factors. Cumulative periprosthetic fracture rates were calculated using Kaplan-Meier analyses and compared with Cox regressions. Subgroup analyses were performed in different age, body mass index, and sex groups.

RESULTS

The 3-month fracture rate in the cemented and cementless TKA groups were 0.02% and 0.04%, respectively. At 10 years, the cumulative fracture rate after cemented TKA was 1.2%, and after cementless was 1.4%. During the study period, there were no significant differences in fracture rates between cemented and cementless TKAs with a hazards ratio 1.14 (confidence interval 0.94 to 1.37, P = .20) at 10 years postoperatively. There were no significant differences in fracture rates between fixation types on subgroup analyses of sex, body mass index, and age groups. Female sex was a risk factor for fracture in both cemented (odds ratio 2.35, P < .001) and cementless TKAs (odds ratio 2.97, P < .001).

CONCLUSIONS

The periprosthetic fracture rates following cemented and cementless TKA surgery are low being approximately 1.2% and 1.4%, respectively at 10 years. There were no significant differences in periprosthetic fracture rates requiring readmission between cemented and cementless TKAs.

LEVEL OF EVIDENCE

III.

A Comparison of the Periprosthetic Fracture Rate of Unicompartmental and Total Knee Replacements: An Analysis of Data of >100,000 Knee Replacements from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man and Hospital Episode Statistics

BACKGROUND

Periprosthetic fractures are rare but devastating complications of knee replacement, often requiring complex surgery with substantial morbidity and mortality. It is not known how the fracture rates after total knee replacement (TKR) and unicompartmental knee replacement (UKR) compare. We performed the first matched study comparing TKR and UKR periprosthetic fracture rates.

METHODS

This study involved 54,215 UKRs and 54,215 TKRs, identified in the National Joint Registry and Hospital Episodes Statistics database, which were propensity score-matched on patient and surgical factors. The International Classification of Diseases, Tenth Revision, (ICD-10) code M96.6 was used to identify periprosthetic fractures at ≤3 and >3 months postoperatively, as well as estimate rates at up to 10 years. Subgroup analyses were performed in different age groups (<55, 55 to 64, 65 to 74, and ≥75 years), body mass index (BMI) categories (normal, 18.5 to <25 kg/m 2 ; overweight, 25 to <30 kg/m 2 ; obese, 30 to <40 kg/m 2 ; and morbidly obese, ≥40 kg/m 2 ), and sexes.

RESULTS

The 3-month fracture rate was 0.09% (n = 50) in the UKR group and 0.05% (n = 25) in the TKR group, with this difference being significant (odds ratio [OR], 2.0; p = 0.004). The rate of fractures occurring at >3 months was 0.32% (n = 171) in the UKR group and 0.61% (n = 329) in the TKR group (OR, 0.51; p < 0.001). At 10 years, the cumulative incidence of fractures was 0.6% after UKR versus 1% after TKR (OR, 0.68; p < 0.001). Fracture rates increased with increasing age, decreasing BMI, and female sex for both UKRs and TKRs.

CONCLUSIONS

The fracture risk was small after both UKR and TKR, with small absolute differences between implant types. During the first 3 postoperative months, the fracture rate after UKR was 0.1% and was about twice as high as that after TKR. However, over the first 10 years, the cumulative fracture rate after TKR was 1% and was almost twice as high as that after UKR. Fracture rates after both UKR and TKR were higher in women, patients ≥75 years of age, and patients with normal weight.

LEVEL OF EVIDENCE

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

Clinical and Functional Results of Cementless Unicompartmental Knee Arthroplasty with a Minimum Follow Up of 5 Years-A Consecutive Cohort of 201 Patients

The number of unicompartmental knee replacements (UKR) is increasing. Alongside various advantages, the revision rate of cemented UKR is higher compared to total knee arthroplasty (TKR). In contrast, cementless fixation shows reduced revision rates, compared to the cemented UKR. However, most of the recent literature is based on designer-dependent studies. In this retrospective, single-center cohort study, we investigated patients who underwent cementless Oxford UKR (OUKR) between 2012 and 2016 in our hospital with a minimum follow-up of five years. Clinical outcome was evaluated using the OKS, AKSS-O, AKSS-F, FFbH-OA, UCLA, SF-36, EQ-5D-3L, FJS, ROM, pain, and satisfaction measures. Survival analysis was performed with reoperation and revision as endpoints. We included 201 patients (216 knees) for clinical evaluation. All outcome parameters increased significantly from pre- to postoperative stages. The five-year survival rate was 96.1% for revision surgery and 94.9% for reoperation. The main reasons for revision were the progression of osteoarthritis, inlay dislocation, and tibial overstuffing. Two iatrogenic tibial fractures appeared. Cementless OUKR shows excellent clinical outcome and high survival rates after five years. The tibial plateau fracture in cementless UKR represents a serious complication and requires modification of the surgical technique.

Impact of keel saw blade design and thickness on the incidence of tibial plateau fracture and tibial implant-loosening in cementless medial UKR

BACKGROUND

Tibial plateau fractures and tibial implant- loosening are severe complications in cementless unicompartmental knee replacement (UKR). The tibial keel preparation is particularly demanding and different saw blades can be used. It was hypothesized that different blade designs and thickness have an influence on the frequency of tibial plateau fractures and implant-loosening in cementless medial UKR.

METHODS

1258 patients with cementless medial UKR were included in this retrospective study between 2013 and 2020. The tibial keel cut was performed either with a double keel saw blade (DKS; 2.8 mm) and added hand guided pick or a mono reciprocating saw blade (RKB) of different thickness (2.5 mm; 2.65 mm; 2.75 mm). Tibial plateau fracture and loosening were demonstrated by standard two-plane radiographs. Tibial implant-loosening was defined as complete radiolucency and implant migration. Fracture and loosening were combined with pain and loss of function.

RESULTS

In 126 patients (10%) the tibial keel was prepared with DKS, in 407 patients (32.4%) with RKB 2.5 mm, in 330 patients (26.2%) with RKB 2.65 mm and in 395 patients (31.4%) with 2.75 mm. In 4 patients (3.17%) with DKS tibial plateau fracture occurred, in 4 patients (0.99%) with 2.5 mm RKB, in 3 patients (0.92%) with 2.65 mm RKB and in 1 patient (0.25%) with 2.75 mm RKB. Significantly fewer fractures occurred with a RKB design (p = 0.007). A negative correlation between fracture incidence and RKB saw blade thickness was found (Spearman-r = - 0.93). No difference for tibial implant-loosening was shown (p = 0.51).

CONCLUSION

Different blade designs and thickness have a significant influence on the incidence of tibial plateau fractures and aseptic tibial implant-loosening. The incidence of tibial plateau fractures in cementless medial UKR can be reduced by changing the design and thickness of the tibial keel saw blade. Greater thickness of RKB leads to significantly fewer tibial plateau fractures while the incidence of implant-loosening is not increasing.

TRIAL REGISTRATION

This study was retrospectively registered and ethical approval was waived by the local ethical committee (No. 2020-1174).

Comparison of five-year clinical outcomes of 524 cemented and cementless medial unicompartmental knee replacements

AIM

To compare the outcomes of cemented and cementless Unicompartmental Knee Replacements (UKR) at 5 years after surgery.

METHODS

262 cemented and 262 cementless medial mobile-bearing UKR, implanted by four high-volume surgeons using identical indications and surgical techniques, were reviewed by independent physiotherapists at 5 years. Survival, Oxford Knee Score (OKS), American Knee Society Score (AKSS), and EQ-5D-5L were assessed. The cementless cohort was mainly implanted after the cemented. Each cohort was divided into early and late sub-groups and compared, to assess if any differences were due to progressive improvement in surgical practice over time.

RESULTS

There were no significant differences between the cohorts for demographics, pre-operative scores, and 5-year revision (0.8%), re-operation (1.5%), and complication rates (5%). The cementless cohort had significantly better 5-year OKS (43v41, p = 0.008), AKSS-Objective (94v90, p = 0.049) and EQ-5D-5L (0.81v0.87, p = 0.0001). Pain sub-scores within OKS, AKSS, and EQ-5D-5L were also significantly better in the cementless cohort, and the differences were proportionally much greater and more significant than differences in their respective overall scores. There was no significant improvement in scores between the early and late subgroups of the cohorts, whereas the 'early-cementless' cohort had significantly better scores than the contemporaneously implanted 'late-cemented' cohort. This suggests that differences found were due to implant type, instead of improved surgical practice over time.

CONCLUSION

Cementless UKR is associated with better clinical outcomes than cemented UKR, which is primarily due to improved pain relief. Both cemented and cementless UKR are safe with low reoperation and complication rates, and a 5-year survival of 99%.

Cementless unicompartmental knee replacement achieves better ten-year clinical outcomes than cemented: a systematic review

PURPOSE

The aim of this study was to report and compare the long-term revision rate, revision indications and patient reported outcome measures of cemented and cementless unicompartmental knee replacements (UKR).

METHODS

Databases Medline, Embase and Cochrane Central of Controlled Trials were searched to identify all UKR studies reporting the ≥ 10 year clinical outcomes. Revision rates per 100 component years [% per annum (% pa)] were calculated by fixation type and then, subgroup analyses for fixed and mobile bearing UKRs were performed. Mechanisms of failure and patient reported outcome measures are reported.

RESULTS

25 studies were eligible for inclusion with a total of 10,736 UKRs, in which there were 8790 cemented and 1946 cementless knee replacements. The revision rate was 0.73% pa (CI 0.66-0.80) and 0.45% pa (CI 0.34-0.58) per 100 component years, respectively, with the cementless having a significantly (p < 0.001) lower overall revision rate. Therefore, based on these studies, the expected 10-year survival of cementless UKR would be 95.5% and cemented 92.7%. Subgroup analysis revealed this difference remained significant for the Oxford UKR (0.37% pa vs 0.77% pa, p < 0.001), but for non-Oxford UKRs there were no significant differences in revision rates of cemented and cementless UKRs (0.57% pa vs 0.69% pa, p = 0.41). Mobile bearing UKRs had significantly lower revision rates than fixed bearing UKRs in cementless (p = 0.001), but not cemented groups (p = 0.13). Overall the revision rates for aseptic loosening and disease progression were significantly lower (p = 0.02 and p = 0.009 respectively) in the cementless group compared to the cemented group (0.06 vs 0.13% pa and 0.10 vs 0.21% pa respectively).

CONCLUSIONS

Cementless fixation had reduced long-term revision rates compared to cemented for the Oxford UKR. For the non-Oxford UKRs, the revision rates of cementless and cemented fixation types were equivalent. Therefore, cementless UKRs offer at least equivalent if not lower revision rates compared to cemented UKRs.

LEVEL OF EVIDENCE

III.

An Early Periprosthetic Fracture of a Cementless Oxford Unicompartmental Knee Arthroplasty: Risk Factors and Mitigation Strategies

Introduction:

The cementless Oxford partial knee arthroplasty is associated with low perioperative complications and good long-term survival rates. However, perioperative fractures remain a serious morbidity for patients.

Case Report:

This case report describes an early post-operative tibial periprosthetic fracture through the keel slot, which we believe may be contributed by the deep implant keel design and the presence of a narrow metaphysis in the Asian knee. The patient subsequently underwent a revision total knee replacement and fixation of the periprosthetic fracture.

Conclusion:

This paper discusses the ways to identify patients at high risk of developing periprosthetic fractures and to minimize such occurrences, including adopting a modified tibial preparation, doing precise saw cuts, and considering a cemented tibial implant.

Femoral migration of the cementless Oxford which caused the bearing dislocation: a report of two cases

BACKGROUND

There are no previous reports on the complications around the femoral component of cementless Oxford unicompartmental knee arthroplasty (UKA). However, we experienced two cases of femoral migration to the proximal side, which caused bearing dislocations after cementless Oxford UKA.

CASE PRESENTATION

Case1. In an 82-year-old woman, bearing dislocation occurred 13 months postoperatively because of femoral migration that was resolved with an revision surgery to cemented component and thicker mobile insert. Case2. In a 52-year-old man, first bearing dislocation occurred 7 months postoperatively. Five months after revising the insert to a thicker one, another dislocation occurred mainly because of the femoral migration. Eventually, a revision to total knee arthroplasty was necessary.

CONCLUSIONS

The inferred main reasons of femoral migration of cementless Oxford were osteoporosis for the first case and early return to high performance sports activity for the second case. Although several merits of using cementless prosthesis, particularly better fixation and lesser radiolucency than cemented prosthesis, have been reported, surgeons should pay attention to the patient's bone quality and advise a slow return to high-level physical activity.

The clinical outcomes of cementless unicompartmental knee replacement in patients with reduced bone mineral density

BACKGROUND

Osteoporosis and osteopenia are conditions characterised by reduced bone mineral density (BMD). There is concern that bone with reduced BMD may not provide sufficient fixation for cementless components which primarily rely on the quality of surrounding bone. The aim of our study was to report the midterm clinical outcomes of patients with reduced BMD undergoing cementless unicompartmental knee replacements (UKR). Our hypothesis was that there would be no difference in outcome between patients with normal bone and those with reduced BMD.

METHODS

From a prospective cohort of 70 patients undergoing cementless UKR surgery, patients were categorised into normal (n = 20), osteopenic (n = 38) and osteoporotic groups (n = 12) based on their central dual-energy X-ray absorptiometry (DEXA) scans according to the World Health Organization criteria. Patients were followed up by independent research physiotherapists and outcome scores; Oxford Knee Score (OKS), Tegner score, American Knee Society Score Functional (AKSS-F) and Objective (AKSS-O) were recorded preoperatively and at a mean of 4 years postoperatively. The prevalence of reoperations, revisions and mortality was also recorded at a mean of 5 years postoperatively.

RESULTS

There were no significant differences in the midterm postoperative OKS (P = 0.83), Tegner score (P = 0.17) and AKSS-O (P = 0.67). However, the AKSS-F was significantly higher (P = 0.04) in normal (90, IQR 37.5) compared to osteoporotic (65, IQR 35) groups. There were no significant differences (P = 0.82) between normal and osteopenic bone (80, IQR 35). The revision prevalence was 5%, 2.6% and 0% in the normal, osteopenic and osteoporotic groups respectively. The reoperation prevalence was 5%, 7.9% and 0% respectively. There were no deaths in any group related to the implant.

CONCLUSIONS

We found that patients with reduced BMD could safely undergo cementless UKR surgery and have similar clinical outcomes to those with normal BMD. However, larger studies with longer follow-up are needed to confirm our findings and ensure that cementless fixation is safe in patients with reduced BMD.