Improved total knee arthroplasty pain outcome when joint gap targets are achieved throughout flexion

Abstract

Purpose Achieving a balanced knee is accepted as an important goal in total knee arthroplasty; however, the deinition of ideal balance remains controversial. This study therefore endeavoured to determine: (1) whether medio-lateral gap balance in extension, midlexion, and lexion are associated with improved outcome scores at one-year post-operatively and (2) whether these relationships can be used to identify windows of optimal gap balance throughout lexion. Methods 135 patients were enrolled in a multicenter, multi-surgeon, prospective investigation using a robot-assisted surgical platform and posterior cruciate ligament sacriicing gap balancing technique. Joint gaps were measured under a controlled tension of 70-90 N from 10°-90° lexion. Linear correlations between joint gaps and one-year KOOS outcomes were investigated. KOOS Pain and Activities of Daily Living sub-scores were used to deine clinically relevant joint gap target thresholds in extension, midlexion, and lexion. Gap thresholds were then combined to investigate the synergistic efects of satisfying multiple targets. Results Signiicant linear correlations were found throughout extension, midlexion, and lexion. Joint gap thresholds of an equally balanced or tighter medial compartment in extension, medial laxity ± 1 mm compared to the inal insert thickness in midlexion, and a medio-lateral imbalance of less than 1.5 mm in lexion generated subgroups that reported signiicantly improved KOOS pain scores at one year (median ∆ = 8.3, 5.6 and 2.8 points, respectively). Combining any two targets resulted in further improved outcomes, with the greatest improvement observed when all three targets were satisied (median ∆ = 11.2, p = 0.002). Conclusion Gap thresholds identiied in this study provide clinically relevant and achievable targets for optimising soft tissue balance in posterior cruciate ligament sacriicing gap balancing total knee arthroplasty. When all three balance windows were achieved, clinically meaningful pain improvement was observed. Level of Evidence Level II.

Sensor-guided gap balance versus manual gap balance in primary total knee arthroplasty: a meta-analysis

“…Omnibot). The OMNIBot (Corin Ltd, Rayham, MA) has been shown to be a reliable tool for delivering different alignment philosophies as well as planning and achieving tibio-femoral coronal balancing [ 43 , 44 ]. The utility of the system is increased when the robot is used in conjunction with a soft-tissue tensioning device—the BalanceBot.…”

Functional Alignment Philosophy in Total Knee Arthroplasty – Rationale and technique for the varus morphotype using a CT based robotic platform and individualized planning

“…The major difference of the FA to previous philosophies is the modification of alignment based on a combination of constitutional bony anatomy and soft-tissue laxity assessment. It is established that instability after knee arthroplasty is a cause for failure [ 10 , 43 ] (particularly in younger patients) [ 44 ], and there is emerging evidence demonstrating that patient pain, and satisfaction scores are related to achieving a target range of tibiofemoral gaps intra-operatively [ 12 , 45 – 47 ]. Wakelin et al used a robotic platform to demonstrate when gap thresholds of an equally balanced compartment or mediolateral imbalance of less than 1.5 mm were achieved with a PS implant, it was associated with significantly improved KOOS pain scores at one-year follow-up [ 12 ].…”

“…It is established that instability after knee arthroplasty is a cause for failure [ 10 , 43 ] (particularly in younger patients) [ 44 ], and there is emerging evidence demonstrating that patient pain, and satisfaction scores are related to achieving a target range of tibiofemoral gaps intra-operatively [ 12 , 45 – 47 ]. Wakelin et al used a robotic platform to demonstrate when gap thresholds of an equally balanced compartment or mediolateral imbalance of less than 1.5 mm were achieved with a PS implant, it was associated with significantly improved KOOS pain scores at one-year follow-up [ 12 ]. Criteria for achieving balance are not yet well defined and may differ based on prosthesis design, i.e., Medial-pivot versus PS, CR constrained designs, or single versus multi-radius curvature femoral components.…”

“…If the HKA angle (calculated as the sum of the femoral coronal alignment and the tibial coronal alignment [ 12 ]) falls outside of 6° varus to 0° valgus for a varus knee, alterations are made to the implant that contributes most to the deformity based on the MPTA and LDFA. A typical plan for a varus knee is presented in Figure 3 .…”

Patient expectations and satisfaction in robotic-assisted total knee arthroplasty: a prospective two-year outcome study

“…Results presented here add to literature supporting improved TKA results when a well-controlled RAS TKA workflow is performed. However, there are many studies both supporting CAS and RAS [27][28][29][30][31][32][33][34][35][36][37][38] as well as reporting no improvement compared to conventional surgery [5,6,[39][40][41][42][43][44][45][46]. The combination of a wide range of study types, patient populations, protocols and confounding factors results in conflicting literature without a clear clinical answer.…”