Joint line changes and outcomes in constrained versus unconstrained total knee arthroplasty for the type II valgus knee
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KNEE
Joint line changes and outcomes in constrained versus unconstrained total knee arthroplasty for the type II valgus knee Hee-Nee Pang • Seng-Jin Yeo • Hwei-Chi Chong Pak-Lin Chin • Shi-Lu Chia • Ngai-Nung Lo
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Received: 6 August 2012 / Accepted: 7 January 2013 Ó Springer-Verlag Berlin Heidelberg 2013
Abstract Purpose The objective of this study was to compare the outcome of constrained and unconstrained primary total knee arthroplasty (TKA) in the management of the valgus deformity. Methods This is a retrospective review of patients with type II valgus knee who underwent primary TKA from 1999 to 2011. There were fifty patients in Group 1 who underwent varus–valgus constrained TKA. They were matched with another fifty patients in Group 2 who underwent unconstrained TKA. Results The mean joint line shift was significantly higher in Group 1 (?8 mm, SD 6 mm) than in Group 2 (?2 mm, SD 3 mm) (p = 0.03). At 2 years, there was no difference in anterior–posterior stability and mediolateral stability according to the Knee Society Score, and patients in Group 2 reported significantly better mean function score of 66.2 (SD 9.3) (mean 48, SD 7.1 in Group 1) (p = 0.002). Two patients (6 %) in Group 1 underwent revision surgery—one for a broken central peg and the other for aseptic loosening. Three patients (2 %) in Group 2 underwent revision surgery—two for global instability and one for poly wear. The estimated survivorship time was 8.3 years for constrained TKA and 12.0 for unconstrained TKA. Conclusion Constrained TKA was associated with more significant joint line changes for the management of valgus arthritic knee, when compared with unconstrained TKA. Level of evidence Retrospective study, Level III.
H.-N. Pang (&) S.-J. Yeo H.-C. Chong P.-L. Chin S.-L. Chia N.-N. Lo Department of Orthopaedic Surgery, Singapore General Hospital, 1 Outram Road, Singapore 169608, Singapore e-mail: [email protected]
Keywords Knee Valgus Constrained Replacement Arthroplasty
Introduction The success of total knee arthroplasty (TKA) depends on restoration of limb alignment, accurate implant positioning and optimal gap balancing [1]. The valgus knee is a challenge in TKA with its complex deformity from lateral femoral bony defects, tight lateral ligamentous structures and stretched out medial soft tissue [2]. Soft tissue balancing is difficult, and surgeons aim to restore mechanical alignment and stability through lateral release [3], tightening the medial structures [4] or constrained implants [5]. The type II valgus knee epitomizes this kind of deformity with lateral compartment bone loss, attenuation of the medial structures and soft tissue asymmetry [2]. There is no consensus on the optimal degree of constrained implants and soft tissue releases for this type of deformity [6]. The implant selection is strongly influenced by the amount of medial laxity [7, 8] and amount of bony deficiency [9]. When an unconstrained implant, such as cruciate-retaining or posterior stabilized prosthesis, is used, lateral soft t
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