Can we define envelope of laxity during navigated knee arthroplasty?
- 578 Downloads
Functional outcomes after knee arthroplasty (TKA) remain poor. The ability to restore the soft tissue envelope intraoperatively may improve such outcomes. The aim of this study was to extend the scope of computer navigation as a tool to quantifying the envelope of laxity during subjective stress testing preoperatively and to quantify the effects of knee replacement and how it changes as a result of ligamentous failure.
Loaded cadaveric legs were mounted on a purpose-built rig. Envelope of laxity was measured in 3 degrees of freedom using computer navigation. Knees were subjectively stressed in varus/valgus, internal/external rotation and anterior draw. This was performed preoperatively, during TKA and after sequential sectioning of ligaments. Real-time data were recorded at 0°, 30°, 60° and 90° of flexion. Mixed effect modelling was used to quantify the effects of intervention on degree of laxity.
In all cases, there was an increase in laxity with increasing flexion or ligament sectioning. Operator and movement cycle had no effect. Insertion of a TKA showed increased stability within the joint, especially in internal/external rotation and anterior drawer. Once the PCL and popliteus were cut, the implant only maintained some rotatory stability; thereafter, the soft tissue envelope failed.
This work has shown a novel way by which computer navigation can be used to analyse soft tissue behaviour during TKA beyond the coronal plane and throughout range of motion. Despite subjective stress testing, our results show reproducible patterns of soft tissue behaviour—in particular a wide range of mid-flexion excursion. It also quantifies the limits within which a cruciate-retaining TKR can maintain knee stability. This functionality may guide the surgeon in identifying and/or preventing soft tissue imbalances intra-operatively, improving functional results.
KeywordsKinematics TKA Soft tissue Cadaveric study Envelope of laxity
This project was supported and undertaken at the Newcastle Surgical Training Centre (Freeman Hospital, Newcastle Upon Tyne, UK). The authors declare no financial arrangements with the fund holding company.
- 7.Cross M (1996) Clinical terminology for describing knee instability. Sports Med Arthrosc Rev 4:313–318Google Scholar
- 16.Kamat YD, Aurakzai KM, Adhikari AR (2012) Computer navigation of soft tissue in total knee replacement J Knee Surg 30. doi: 10.1055/s-0032-1322600
- 19.Lanting BA, Snider MG, Chess DG (2012) Effect of polyethylene component thickness on range of motion and stability in primary total knee arthroplasty. Orthopedics 35:170–174Google Scholar
- 21.Lombard WP, Abbott FM (1907) The mechanical effects produced by the contraction of individual muscles of the thigh of the frog. Am J Physiol 20:1–60Google Scholar
- 23.Matsumoto T, Muratsu H, Kubo S, Mizuno K, Kinoshita K, Ishida K, Matsushita T, Sasaki K, Tei K, Takayama K, Sasaki H, Oka S, Kurosaka M, Kuroda R (2011) Soft tissue balance measurement in minimal incision surgery compared to conventional total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 19:880–886PubMedCrossRefGoogle Scholar
- 25.Norris M, Gill K, Karadaglis D, Chauhan S (2009) The envelope of laxity and balancing of total knee replacement using navigation. J Bone Joint Surg Br 91B:426Google Scholar
- 33.The national joint registry 8th annual report. Sept 2011, pp 95Google Scholar