POLYETHYLENE STRESSES IN UNICOMPARTMENTAL KNEE REPLACEMENTS DURING A STEP-UP ACTIVITY: A COMPARISON BETWEEN A FIXED AND MOBILE BEARING

Abstract Purpose Given an increasingly overweight population, unicompartmental knee replacements (UKRs) are being performed in patients with higher body mass indices (BMIs). There are concerns that cemented fixation will not last. Cementless fixation may offer a solution, but the long term results in different BMI groups has not been assessed. We studied the effect of BMI on the outcomes of cementless UKRs. Methods A prospective cohort of 1000 medial cementless mobile-bearing UKR with a mean follow up of 6.6 years (SD 2.7) were analysed. UKRs were categorised into four BMI groups: (1) ≥ 18.5 to < 25 kg/m2 (normal), (2) 25 to < 30 kg/m2 (overweight), (3) 30 to < 35 kg/m2 (obese class 1) and (4) ≥ 35 kg/m2 (obese class 2). Implant survival was assessed using endpoints reoperation and revision. Functional outcomes were assessed. Results Ten-year cumulative revision rate for the normal (n = 186), overweight (n = 434), obese class 1 (n = 213) and obese class 2 (n = 127) groups were 1.8% (CI 0.4–7.4), 2.6% (CI 1.3–5.1), 3.8% (CI 1.5–9.2) and 1.7% (CI 0.4–6.8) with no significant differences between groups (p = 0.79). The 10-year cumulative reoperation rates were 2.7% (CI 0.8–8.2), 3.8% (CI 2.2–6.6), 5.2% (CI 2.5–10.7) and 1.7% (CI 0.4–6.8) with no significant differences between groups (p = 0.44). The 10-year median Oxford Knee Score were 43.0, 46.0, 44.0 and 38.0 respectively. Conclusion Cementless mobile-bearing UKR has low 10-year reoperation and revision rates across in all BMI groups, and there are no significant differences between the groups. Although higher BMI groups had slightly worse functional outcomes, the improvement in function compared to preoperatively tended to be better. This study suggests that BMI should not be considered a contraindication for the cementless mobile-bearing UKR.

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Posterior Bearing Overhang Following Medial and Lateral Mobile Bearing Unicompartmental Knee Replacements

Journal of Orthopaedic Research® ◽

10.1002/jor.24339 ◽

2019 ◽

Vol 37 (9) ◽

pp. 1938-1945

Author(s):

Benjamin Richard Martin ◽

Elise C. Pegg ◽

Bernard H. Duren ◽

Hasan R. Mohammad ◽

Hemant G. Pandit ◽

...

Keyword(s):

Mobile Bearing ◽

Unicompartmental Knee ◽

Knee Replacements

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The effect of age on the outcomes of cementless mobile bearing unicompartmental knee replacements

Knee Surgery Sports Traumatology Arthroscopy ◽

10.1007/s00167-020-06428-0 ◽

2021 ◽

Cited By ~ 1

Author(s):

Hasan Raza Mohammad ◽

Stephen Mellon ◽

Andrew Judge ◽

Christopher Dodd ◽

David Murray

Keyword(s):

Functional Outcomes ◽

Age Groups ◽

Mobile Bearing ◽

Level Of Evidence ◽

Unicompartmental Knee ◽

Age At Surgery ◽

Knee Replacements ◽

Cumulative Revision Rate ◽

Reoperation Rates ◽

Effect Of Age

Abstract Purpose Unicompartmental Knee Replacements (UKR) are being performed in patients with increasing demands and life expectancies with surgical concerns that cemented fixation will not last. Cementless fixation may offer a solution, but the results in different age groups have not been assessed. The effect of age at surgery on the outcomes of cementless UKRs was investigated. Methods A prospective cohort of 1000 medial cementless mobile bearing UKR were analysed. Patients were categorised into four age groups (< 55, 55 to < 65, 65 to < 75 and ≥ 75 years). Implant survival was assessed using endpoints reoperation, revision and major revision requiring revision knee replacement components. Functional outcomes were assessed. Results 10 year cumulative revision rate for the < 55, 55 to < 65, 65 to < 75 and ≥ 75 groups were 2.1% (CI 0.6–6.1), 1.8% (CI 0.6–5.3), 3.2% (CI 1.5–6.5) and 4.1% (1.7–9.6) with no differences between groups (p = 0.52). Two of the 22 revisions were considered major. The 10 year cumulative reoperation rates were 4.5% (CI 2.0–10.0), 3.0% (CI 1.3–6.5), 3.8% (CI 2.0–7.1) and 4.1% (CI 1.7–9.6) with no differences between groups (p = 0.81). The 10 year median Oxford Knee Scores were 42.5, 46.5, 45 and 42.5, respectively. The 10 year median Objective American Knee Society Scores were 95 for all age groups. Conclusion The cementless mobile bearing UKR has low reoperation and revision rates and similar functional outcomes in all age groups. Cementless UKR should be used in all age groups and age should not be considered a contraindication. Level of evidence III.

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Early Results of Lateral Unicompartmental Knee Replacements: A Comparison of Fixed and Mobile Bearing Prosthesis

Arthroscopy The Journal of Arthroscopic and Related Surgery ◽

10.1016/j.arthro.2013.07.183 ◽

2013 ◽

Vol 29 (10) ◽

pp. e143

Author(s):

Narayana Prasad ◽

Ben Marson ◽

Mark Lewis

Keyword(s):

Mobile Bearing ◽

Unicompartmental Knee ◽

Early Results ◽

Knee Replacements

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A Soft- Tissue Injury Diagnosis in Knee Replacement Patients cannot be made without a Plain Radiograph

Journal of Orthopaedic Case Reports ◽

10.13107/jocr.2021.v11.i04.2150 ◽

2021 ◽

Vol 11 (4) ◽

Author(s):

Rute Castelhano ◽

Sunny Deo

Keyword(s):

Soft Tissue ◽

Knee Replacement ◽

Plain Radiograph ◽

Mobile Bearing ◽

Definitive Treatment ◽

Unicompartmental Knee Replacement ◽

Unicompartmental Knee ◽

Patient Reported ◽

Knee Replacements

Introduction: The design of some knee replacements includes the use of a mobile polyethylene bearing which can potentially dislocate away from the main bearing surfaces. This is particularly the case in unicompartmental or partial knee replacements (UKRs), and the most widely used UKR currently has this feature. Bearing dislocations are typically very painful and disabling, but not always, as in the case we present. Case Report: We report the case of a patient presenting at a 1 -year follow- up following a mobile bearing UKR. At this consultation, the patient reported a smooth initial recovery but with on-going pain and swelling in the posterior aspect of his knee for 3 months, diagnosed as a soft- tissue strain. Results: Radiographs at 1 year follow-up appointment showed that the polyethylene insert was dislocated posteriorly towards the popliteal fossa with metal components in direct contact. At revision surgery, this was confirmed as a chronic dislocation with severe metallosis requiring revision to a total knee replacement. Conclusion: We report a case of a posterior dislocation of a mobile polyethylene bearing of a partial / unicompartmental knee replacement UKR with delayed definitive treatment due to mis-diagnosis at the time of onset of symptoms and signs. The key lesson is that plain radiographs should be obtained promptly for any local issue in knee replacement patients. Keywords: Unicompartmental knee replacement, metallosis, mobile bearing dislocation, soft tissue injuries.

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