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Changes in patella tendon length over 5 years after different types of knee arthroplasty

  • Knee
  • Published:
Knee Surgery, Sports Traumatology, Arthroscopy Aims and scope

Abstract

Purpose

Post-operative shortening of the patellar tendon resulting in an abnormally low-lying patella has been described previously, but the degree of change in patella tendon length over time and extent of its progression after different types of knee arthroplasties remains unknown. This study assesses the incidence of patella tendon length change following lateral unicompartmental knee arthroplasty (UKA), medial UKA, and total knee arthroplasty (TKA), and its impact on patient-reported outcome at 5 years post-surgery.

Methods

Immediate post-operative, 1- and 5-year radiographs were reviewed for 50 patients undergoing each operation (n = 150), with the Insall–Salvati ratio used as a measure of patella tendon length. Clinical outcome was assessed using the Oxford Knee Score (OKS).

Results

At 5-year follow-up, no significant change in patella tendon length was found following medial UKA (1.07–1.05), whilst a significant shortening was found after TKA (1.02–0.96), and a significant lengthening found after lateral UKA (1.02–1.05). For the UKA groups, no further change in tendon length was observed after the first year post-surgery, whereas the TKA group continued to shorten between years one and five. OKS was significantly better in the UKA groups as compared to TKA group. Change in patella tendon length within individual groups did not correlate with OKS at 5 years.

Conclusion

Patella tendon length shortening is more prevalent in TKAs, whilst lengthening is more prevalent in lateral UKAs. Despite the vertical incision through the patella tendon, lateral UKAs do not cause increased tendon shortening at 5 years post-surgery. However, in the medium term, changes in patella tendon length do not affect patient-reported outcome.

Level of evidence

Retrospective, comparative study, Level III.

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Abbreviations

TKA:

Total knee arthroplasty

UKA:

Unicompartmental knee arthroplasty

ACL:

Anterior cruciate ligament

IS:

Insall–Salvati

OKS:

Oxford Knee Score

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Author’s contributions

GD performed the radiographic assessment, collated the data, and drafted the manuscript. BvD developed the software for radiographic assessment and provided mentoring and teaching regarding the use of the software. MS also performed the radiographic assessment. PGR and JM collected suitable patients and provided their radiographs and clinical information. PM participated in the study design and coordination along with DM and HP.

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Authors and Affiliations

  1. Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK

    Gareth Sion Davies, Ben van Duren, Matthew Shorthose, Patrick Garfjeld Roberts, Andrew P. Monk, David W. Murray & Hemant G. Pandit

  2. Royal Berkshire Hospital, Reading, UK

    John R. Morley

Authors
  1. Gareth Sion Davies
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  2. Ben van Duren
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  3. Matthew Shorthose
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  4. Patrick Garfjeld Roberts
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  6. Andrew P. Monk
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  7. David W. Murray
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  8. Hemant G. Pandit
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Correspondence to Gareth Sion Davies.

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The authors declare that they have no competing interests.

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Davies, G.S., van Duren, B., Shorthose, M. et al. Changes in patella tendon length over 5 years after different types of knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 24, 3029–3035 (2016). https://doi.org/10.1007/s00167-016-4170-6

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  • DOI: https://doi.org/10.1007/s00167-016-4170-6

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