Development of reference charts for monitoring quadriceps strength with handheld dynamometry after total knee arthroplasty

Abstract

Purpose: To develop reference charts that describe normative quadriceps strength recovery after total knee arthroplasty (TKA) as measured by handheld dynamometry (HHD).Materials and Methods: We conducted a retrospective analysis of post-TKA quadriceps strength recovery in a longitudinal dataset consisting of both clinical and research HHD data. We created sex-specific models for recovery using Generalized Additive Models for Location, Scale, and Shape. We created reference charts from the models to display the recovery of population centiles over the first six postoperative months.Results: A total of 588 patient records with 1176 observations were analyzed. Reference charts for both sexes demonstrated a rapid increase in quadriceps strength over the first 60 postoperative days followed by a more gradual increase over the next 120 days. Males appeared to demonstrate faster recovery and greater strength on average compared to females. The quadriceps strength recovery of three female patient records was plotted on the reference chart to illustrate the charts' potential clinical utility.Conclusions: These reference charts provide normative data for quadriceps strength recovery after TKA as assessed by HHD. The reference charts may augment clinicians' ability to monitor and intervene upon quadriceps weakness-a pronounced and debilitating post-TKA impairment-throughout rehabilitation.Implications for RehabilitationHandheld dynamometry (HHD) is an objective and clinically feasible method for assessing muscle strength, but normative HHD values are lacking for quadriceps strength recovery after total knee arthroplasty (TKA).We created sex-specific reference charts which provide normative quadriceps strength HHD values for the first 180 days after TKA.These reference charts may improve clinicians' ability to monitor and intervene upon post-TKA quadriceps strength deficits.

Keywords: Total knee arthroplasty; clinical monitoring; handheld dynamometry; quadriceps strength; rehabilitation.

Appendix Figure 1.

Female reference chart sensitivity analysis for repeated measures. The full model (black) is plotted against the limited model with only one measurement per patient (light blue). The models demonstrate close agreement across centiles which suggests the full model is robust to repeated measurements. The mean difference between the models across timepoints is 0.09% bodyweight for the 10^th centiles, 0.23% bodyweight for the 50^th centiles, and 0.30% bodyweight for the 90^th centiles.

Appendix Figure 2.

Male reference chart sensitivity analysis for repeated measures. The full model (black) is plotted against the limited model with only one measurement per patient (light blue). The models demonstrate close agreement across centiles which suggests the full model is robust to repeated measurements. The mean difference between the models across timepoints is 0.08% bodyweight for the 10^th centiles, 0.28% bodyweight for the 50^th centiles, and 0.37% bodyweight for the 90^th centiles.

Figure 1.

Flow diagram and demographics for data included in final analysis

Figure 2.

Reference chart describing post-TKA quadriceps strength recovery for females. The centiles for female quadriceps strength recovery (5^th, 10^th, 25^th, 50^th, 75^th, 90^th, and 95^th) are plotted continuously over the first 180 postoperative days.

Figure 3.

Reference chart describing post-TKA quadriceps strength recovery for males. The centiles for male quadriceps strength recovery (5^th, 10^th, 25^th, 50^th, 75^th, 90^th, and 95^th) are plotted continuously over the first 180 postoperative days.

Figure 4.

Reference chart with example female patient cases. The observed quadriceps strength values are plotted for Patient A (green), Patient B (red), and Patient C (purple) over the first 60 postoperative days.