Total knee arthroplasty (TKA) is highly successful due to pain reduction, patient satisfaction, and increased range of motion (ROM) during activities of daily living (ADL). ROM recovery is critical for successful outcomes, however ROM values are typically captured during routine physical therapy (PT) appointments via simplified measures (e.g. goniometric maximum passive ROM). These measures are imprecise, potentially neglecting patients’ home experiences. Accordingly, improved measurement methods are necessary to realistically represent ROM recovery. A validated inertial measurement unit (IMU) method continuously capturing knee ROM was deployed assessing knee ROM recovery during PT appointments and during patients’ routine daily experiences. Our objectives were to 1) continuously capture knee ROM pre-/post-TKA via IMUs and 2) divide each day's data to PT/non-PT segments comparing ‘gold standard’ ROM measurements (PT periods) with non-invasive home measurements (non-PT periods). Given patients are verbally/physically encouraged during PT, we hypothesized PT and non-PT metrics would be significantly different including 1) greater kinematics, 2) shorter times, and 3) greater activity level during PT compared to non-PT. Following IRB approval, IMUs captured long duration, continuous (8–12 hours/day, ∼50 days) knee ROM pre-/post-TKA. Post-TKA metrics were subdivided to PT/non-PT time periods including maximum ROM, gait phase ROMs (stance/swing), gait times (stride/stance/swing), and activity level. Clinical ROM and patient reported outcome measures (PROMs) were also captured before/after TKA. Statistical comparisons were completed between pre-TKA, post-TKA PT, and post-TKA non-PT metrics. Correlation analyses were completed between IMU, clinical ROM, and PROMs.Introduction
Methods
With many stakeholders, healthcare decisions are complex. However, patient interests should be prioritized. This maximizes healthcare value (quality divided by cost), simultaneously minimizing costs (objective) and maximizing quality (subjective). Unfortunately, even ‘high value’ procedures like total knee arthroplasty (TKA) suffer from recovery assessment subjectivity (i.e. high assessment variability) and increasing costs. High TKA costs and utilization yield high annual expenditures (∼$22B), including postoperative physical therapy (PT) accounting for ∼10% of total costs (∼$2.3B annually). Post-TKA PT is typically homogenous across subjects ensuring most recover, however recent work shows outcomes unimpacted by PT. Accordingly, opportunities exist improving healthcare value by simultaneously reducing unnecessary PT expenditures and improving outcomes. However, discerning recovery completion relies on discrete ROM measures captured clinically and subjective clinician experience (i.e. intuition about recovery). Accordingly, our goal was developing objective post-TKA performance assessment methods utilizing gait knee ROM and statistical analyses to categorize patient recovery (‘accelerated,’ ‘delayed,’ or ‘normal’). We first established statistical reasons for current post-TKA rehabilitation including risk-reward tradeoffs between incorrectly ascribing ‘poor recovery’ to well-recovering patients (T1 error) or ‘good recovery’ to poorly-recovering patients (T2 error) using methods described by Mudge et al. and known TKA volumes/rehabilitation costs. Next, previously captured gait ROM data from well-healed patients was utilized establishing standard recovery curves. These were then utilized to assess newly captured patient recovery. Following IRB approval, we prospectively captured gait ROM from 10 TKA patients (3M, 69±13 years) 1-week pre-TKA and 6-weeks immediately post-TKA. Performance was compared to recovery curves via control charts/Shewhart rules (daily performance) as well as standard deviation thresholds (weekly performance) establishing recovery as ‘accelerated,’ ‘delayed,’ or ‘normal.’ The categorization was extrapolated to US TKA population and savings/expenses quantified. Statistical analyses were performed in Minitab with statistical significance set to α<0.05.Introduction
Methods
For nearly 58% of total knee arthroplasty (TKA) revisions, the reason for revision is exacerbated by component malalignment. Proper TKA component alignment is critical to functional outcomes/device longevity. Several methods exist for orthopedic surgeons to validate their cuts, however, each has its limitations. This study developed/validated an accurate, low-cost, easy to implement first-principles method for calculating 2D (sagittal/frontal plane) tibial tray orientation using a triaxial gyroscope rigidly affixed to the tibial plateau of a simulated leg jig and validated 2D tibial tray orientation in a human cadaveric model. An initial simulation assessed error in the sagittal/frontal planes associated with all geometric assumptions over a range of positions (±10°, ±10°, and −3°/0°/+3° in the sagittal, frontal, and transverse planes, respectively). Benchtop experiments (total positions - TP, clinically relevant repeated measures - RM, novice user - NU) were completed using a triaxial gyroscope rigidly affixed to and aligned with the tibial tray of the fully adjustable leg-simulation jig. Finally, two human cadaveric experiments were completed. A similar triaxial gyroscope was mounted to the tibial tray of a fresh frozen human cadaver to validate sagittal and frontal plane tibial tray orientation. In cadaveric experiment one, three unique frontal plane shims were utilized to measure changes in frontal plane angle. In cadaveric experiment two, measurements using the proprosed gyroscopic method were compared with computer navigation at a series of positions. For all experiments, one rotation of the leg was completed and gyroscopic data was processed through a custom analysis algorithm.Introduction
Methods
Subluxation and dislocation are frequently cited reasons for THA revision. For patients who cannot accommodate a larger femoral head, an offset liner may enhance stability. However, this change in biomechanics may impact the mechanical performance of the bearing surface. To our knowledge, no studies have compared wear rates of offset and neutral liners. Herein we radiographically compare the in-vivo wear performance of 0mm and 4mm offset acetabular liners. Two cohorts of 40 individuals (0mm, 4mm offset highly crosslinked acetabular liners, respectively) were selected from a single surgeon's consecutive caseload. All patients received the same THA system via the posterior approach. AP radiographs were taken at 6-week (‘pre’) and 5-year (‘post’) postoperative appointments. Patients with poor radiograph quality were excluded (n0mm=5, n4mm=4). Linear and volumetric wear were quantified according to Patent US5610966A. Briefly, images were processed in computer aided design (CAD) software. Differences in vector length between the center of the femoral head and the acetabular cup (pre- and post-vector, Figure 1) allow for calculation of linear wear and wear rate. The angle (β) between the linear wear vector and the cup inclination line was quantified (Figure 1). Patients with negative β were excluded from volumetric analyses (n0mm=11, n4mm=7). Volumetric wear was accordingly calculated accounting for wear vector direction. The results from three randomly selected patients were compared to results achieved using the “Hip Analysis Suite” software package (UChicagoTech).Introduction
Methods
