Tibial forces are more useful than varus‐valgus laxities for identifying and correcting overstuffing in kinematically aligned total knee arthroplasty

Knee Surg Sports Traumatol Arthrosc

Hull

2022

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Purpose Surgeons performing total knee arthroplasty (TKA) are interested in the accuracy and time it takes to make the four femoral resections that determine the setting of the femoral component. A method for quantifying the error of each resection is the thickness, measured by a caliper, minus the femoral target. The present study tested the hypothesis that the mean deviation of the resection from the femoral target, the percentage of resections with a deviation of ± 0.5, 1.0, 1.5, and 2.0 mm, and the time to complete the femoral cuts were not different between experienced (E) and less-experienced (LE) surgeons performing unrestricted caliper verified kinematically aligned (KA) TKA with manual instruments. Methods This study analyzed intraoperative verification worksheets from 203 patients treated by ten E surgeons and 58 patients treated by four LE surgeons. The worksheet recorded (1) the thickness of the femoral target for the distal medial (DM), distal lateral (DL), posterior medial (PM), and posterior lateral (PL) resections and the caliper thickness of the resections with a resolution of 0.5 mm, and (2) the time to complete them. The most accurate resection has a mean difference ± standard deviation of 0 ± 0.0 mm. Results The accuracy of the 1044 initial resections (261 patients) was significantly closer to the femoral target for E vs. the LE surgeons: 0.0 ± 0.4 vs. − 0.3 ± 0.5 for the DM, 0.0 ± 0.5 vs. − 0.4 ± 0.6 for the DL, − 0.1 ± 0.5 vs. − 0.2 ± 0.5 PM, and − 0.1 ± 0.5 vs. − 0.4 ± 0.6 for the PL resections (p ≤ 0.0248). E surgeons completed the femoral resections in 12 min; 5 min faster than LE surgeons (p < 0.0001). Conclusions Because the mean difference in femoral resections with manual instruments for E vs. LE surgeons was < 0.5 mm which is within the caliper’s resolution, differences in accuracy were not clinically relevant. Surgeons exploring other alignment options and robotic, navigation, and patient-specific instrumentation might find these values helpful when deciding to change. Level of evidence III; case–control study.

Section: Discussionmentioning

confidence: 99%

Negligible effect of surgeon experience on the accuracy and time to perform unrestricted caliper verified kinematically aligned TKA with manual instruments

Knee Surg Sports Traumatol Arthrosc

Hull

2022

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“…Compared to the mean operative time of 116 min for MA TKA by four fellowship-trained arthroplasty surgeons at an urban, academic institution, the IE surgeon was more efficient [ 28 ]. In addition, a senior surgeon using an electronic sensor took 109 min to balance an MA TKA; however, in 38 min less time, the caliper-verified KA technique, by default, restored the native medial and lateral tibial compartment forces without ligament release [ 12 , 13 ]. Hence, surgeons switching to KA might find these comparisons comforting.…”

Section: Discussionmentioning

confidence: 99%

“…Correct distal and posterior femoral resections set the femoral component coincident with the patient’s pre-arthritic joint lines. Resection errors resulting in 1- and 2- degree deviations from the femoral and tibial joint lines cause high medial and lateral tibial compartment forces relative to the native knee [ 10 , 11 , 12 , 13 ]. The surgeon determines the accuracy, or deviation from the planned resection, by measuring the thickness of the distal and posterior medial and lateral femoral resections with a caliper and subtracting the thickness of the corresponding condyle of the femoral component, 2 mm for cartilage wear, and 1 mm for the kerf of the blade [ 14 , 15 ].…”

Section: Introductionmentioning

confidence: 99%

A Surgeon That Switched to Unrestricted Kinematic Alignment with Manual Instruments Has a Short Learning Curve and Comparable Resection Accuracy and Outcomes to Those of an Experienced Surgeon

Dhaliwal

et al. 2022

JPM

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After starting an orthopedic practice, a surgeon with a fellowship in mechanically aligned (MA) TKA initiated this study to characterize their learning curve after they switched to unrestricted kinematic alignment (KA) TKA using manual instruments. Accordingly, the present study determined for the inexperienced (IE) surgeon the number of cases required to achieve consistent femoral resections and operating times, and whether the femoral resection accuracy, patient-reported outcome measures (PROMs), and component alignment were different from an experienced (E) surgeon. This prospective cohort study analyzed the IE surgeon’s first 30 TKAs, all performed with KA, and 30 consecutive KA TKAs performed by an E surgeon. The resection accuracy or deviation was the calipered thickness of the distal and posterior medial and lateral femoral resections minus the planned resection thickness, which was the thickness of the corresponding condyle of the femoral component, minus 2 mm for cartilage wear, and 1 mm for the kerf of the blade. Independent observers recorded the femoral resection thickness, operative times, PROMs, and alignment. For each femoral resection, the deviation between three groups of patients containing ten consecutive KA TKAs, was either insignificant (p = 0.695 to 1.000) or within the 0.5 mm resolution of the caliper, which indicated no learning curve. More than three groups were needed to determine the learning curve for the operative time; however, the IE surgeon’s procedure dropped to 77 min for the last 10 patients, which was 20 min longer than the E surgeon. The resection deviations of the IE and E surgeon were comparable, except for the posterolateral femoral resection, which the IE surgeon under-resected by a mean of −0.8 mm (p < 0.0001). At a mean follow-up of 9 and 17 months, the Forgotten Joint Score, Oxford Knee Score, KOOS, and the alignment of the components and limbs were not different between the IE and E surgeon (p ≥ 0.6994). A surgeon that switches to unrestricted KA with manual instruments can determine their learning curve by computing the deviation of the distal and posterior femoral resections from the planned resection. Based on the present study, an IE surgeon could have resection accuracy, post-operative patient outcomes, and component alignment comparable to an E surgeon.

“…First, component malposition was unlikely, as unrestricted caliper-verified KA sets the components within 0 ± 0.5 mm of the patient's pre-arthritic femoral and tibial joint lines. Components set coincident to the native joint surface restore the resting lengths of the collateral and posterior cruciate ligaments, which restores native medial and lateral tibial compartment forces without the morbidity of ligament release [18][19][20][21][22][23]. Resurfacing the knee reduces the risk of kinematic conflict from component malposition, enabling the MUA to regain motion.…”

Section: Discussionmentioning

confidence: 99%

Excellent and Good Results Treating Stiffness with Early and Late Manipulation after Unrestricted Caliper-Verified Kinematically Aligned TKA

Shekhar

et al. 2022

JPM

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Manipulation under anesthesia (MUA) for stiffness within 6 to 12 weeks after mechanically aligned total knee arthroplasty (TKA) generally yields better outcome scores than an MUA performed later. However, the timing of MUA after unrestricted, caliper-verified, kinematically aligned (KA) TKA remains uncertain. A retrospective review identified 82 of 3558 (2.3%) KA TKA patients treated with an MUA between 2010 and 2017. Thirty patients treated with an MUA within 3 months of the TKA (i.e., early) and 24 in the late group (i.e., >3 months) returned a questionnaire after a mean of 6 years and 5 years, respectively. Mean outcome scores for the early vs. late group were 78 vs. 62 for the Forgotten Joint Score (FJS) (p = 0.023) and 42 vs. 39 for the Oxford Knee Score (OKS) (p = 0.037). Subjectively, the early vs. late group responses indicated that 83% vs. 67% walked without a limp, 73% vs. 54% had normal extension, and 43% vs. 25% had normal flexion. An MUA within 3 months after unrestricted KA TKA provided excellent FJS and OKS at final follow-up relative to a late MUA. A late MUA performed after 3 months is worth consideration because of the good FJS and OKS scores, albeit with a risk of a persistent limp and limitation in knee extension and flexion.