In a typical osteoarthritic knee with varus deformity, distal femoral resection based off the worn medial femoral condyle may result in an elevated joint line. In a setting of fixed flexion ...contracture, the surgeon may choose to resect additional distal femur to obtain extension, thus purposefully raising the joint line. However, the biomechanical effect of raising the joint line is not well recognized.
(1) What is the effect of the level of the medial joint line (restored versus raised) on coronal plane stability of a TKA? (2) Does coronal alignment technique (mechanical axis versus kinematic technique) affect coronal plane stability of the knee? (3) Can the effect of medial joint-line elevation on coronal plane laxity be predicted by an analytical model?
A TKA prosthesis was implanted in 10 fresh frozen nonarthritic cadaveric knees with restoration of the medial joint line at its original level (TKA0). Coronal plane stability was measured at 0°, 30°, 60°, 90°, and 120° flexion using a navigation system while applying an instrumented 9.8-Nm varus and valgus force moment. The joint line then was raised in two steps by recutting the distal and posterior femur by an extra 2 mm (TKA2) and 4 mm (TKA4), downsizing the femoral component and, respectively, adding a 2- and a 4-mm thicker insert. This was done with meticulous protection of the ligaments to avoid damage. Second, a simplified two-dimensional analytical model of the superficial medial collateral ligament (MCL) length based on a single flexion-extension axis was developed. The effect of raising the joint line on the length of the superficial MCL was simulated.
Despite that at 0° (2.2° ± 1.5° versus 2.3° ± 1.1° versus 2.5° ± 1.1°; p = 0.85) and 90° (7.5° ± 1.9° versus 9.0° ± 3.1° versus 9.0° ± 3.5°; p = 0.66), there was no difference in coronal plane laxity between the TKA0, TKA2, and TKA4 positions, increased laxity at 30° (4.8° ± 1.9° versus 7.9° ± 2.3° versus 10.2° ± 2.0°; p < 0.001) and 60° (5.7° ± 2.7° versus 8.8° ± 2.9° versus 11.3° ± 2.9°; p < 0.001) was observed when the medial joint line was raised 2 and 4 mm. At 30°, this corresponds to an average increase of 64% (3.1°; p < 0.01) in mid-flexion laxity with a 2-mm raised joint line and a 111% (5.4°; p < 0.01) increase with a 4-mm raised joint line compared with the 9-mm baseline resection. No differences in coronal alignment were found between the knees implanted with kinematic alignment versus mechanical alignment at any flexion angle. The analytical model was consistent with the cadaveric findings and showed lengthening of the superficial MCL in mid-flexion.
Despite a well-balanced knee in full extension and at 90° flexion, increased mid-flexion laxity in the coronal plane was evident in the specimens where the joint line was raised.
When recutting the distal and posterior femur and downsizing the femoral component, surgeons should be aware that this action might increase the laxity in mid-flexion, even if the knee is stable at 0° and 90°.
Total knee arthroplasty (TKA) implants have continued to evolve to accommodate new understandings of knee mechanics. The medial-pivot implant is a newer design, which is intended to limit ...anterior-posterior translation in the medial compartment while allowing lateral compartment translation. However, evidence for a generalized medial-pivot characteristic across all activities is limited. The purpose of the study was to quantify and compare in vivo knee joint kinematics using high-speed stereo radiography during activities of daily living in patients who have undergone a TKA with a cruciate sacrificing medial-pivot implant to age-matched and sex-matched native controls.
Fifteen participants (7 patients, 4 women, mean age 70 years and 8 nonsymptomatic controls, 4 women, mean age 64 years) performed 6 functional tasks in high-speed stereo radiography: deep-knee lunge, chair rise, step down, gait, gait with 90° turn, and seated knee extension. Translational differences between groups (surgical versus control) were assessed for the medial and lateral condyle, while pivot location was normalized to subject-specific tibial plateau geometry.
The surgical cohort displayed a more constrained medial condyle that provided greater stability of the medial compartment and did not result in the paradoxical anterior translation at mid-flexion angles during weight-bearing activities, but was associated with less condylar translation than native knees. Additionally, the transverse tibial pivot location occurs most commonly in the middle third of the tibial plateau and secondarily on the medial third.
Some variability in pivot location occurs between activities and is more in nonsymptomatic, native knee controls.
Pain catastrophizing contributes to acute and long-term pain after knee arthroplasty (KA), but the association between pain catastrophizing and physical function is not clear. We examined the ...association between preoperative pain catastrophizing and physical function one year after surgery, as well as differences in physical function, pain and general health in two groups of patients with high and low preoperative pain catastrophizing score.
We included 615 patients scheduled for KA between March 2011 and December 2013. Patients completed The Pain Catastrophizing Scale (PCS) prior to surgery. The Oxford Knee Score (OKS), Short Form-36 (SF-36) and the EuroQol-5D (EQ-5D) were completed prior to surgery, and 4 and 12 months after the surgery.
Of the 615 patients, 442 underwent total knee arthroplasty (TKA) and 173 unicompartmental knee arthroplasty (UKA). Mean age was 67.3 (SD: 9.7) and 53.2% were females. Patients with PCS > 21 had statistically significantly larger improvement in mean OKS for both TKA and UKA than patients with PCS < 11; 3.2 (95% CI: 1.0, 5.4) and 5.4 (95% CI: 2.2, 8.6), respectively. Furthermore, patients with preoperative PCS > 21 had statistically significantly lower OKS, SF-36 and EQ-5D and higher pain score than patients with PCS < 11 both preoperatively and 4 and 12 months postoperatively.
Patients with high levels of preoperative pain catastrophizing have lower physical function, more pain and poorer general health both before and after KA than patients without elevated pain catastrophizing.
Purpose
Tibial plateau fractures are serious complications of Oxford mobile-bearing unicompartmental knee arthroplasty (OUKA). This study examined where the fracture lines arises and evaluated the ...keel–cortex distances (KCDs) using three-dimensional computed tomography (3D-CT) and the effects of technical error (assessed by tibial component positions) and proximal tibial morphology on the KCDs.
Methods
This retrospective study included 217 OUKAs with cementless tibial components. Fifteen patients had tibial fractures after surgery. Anterior and posterior KCDs and fracture line origins were assessed using 3D-CT postoperatively. Proximal tibial morphology was assessed using the medial eminence line (MEL), which runs parallel to the tibial axis and passes through the tip of the medial intercondylar eminence of the tibia on long-leg anteroposterior radiograph. Knees had overhanging medial tibial condyle if the MEL passed medially to the medial tibial cortex. KCDs were compared between patients with/without fractures. Tibial component positions were evaluated, considering effects of tibial morphologies and component positions on fracture prevalence and KCDs.
Results
Fracture lines were found between the keel and posterior cortex in 12/15 patients. Posterior KCDs were significantly shorter in patients with fractures than in patients without (2.7 ± 1.6 mm vs 5.2 ± 1.7 mm,
P
< 0.001). Patients with medial overhanging condyles were more likely to have fracture (10/51 vs 5/166,
P
< 0.001) and had significantly shorter posterior KCD than those without (3.6 ± 1.5 mm vs 5.5 ± 1.8 mm,
P
< 0.001). Patients with tibial component that was set too medial, low, and valgus had higher rates of fracture than those without (7/39 vs 8/178,
P
= 0.008). Medial (
r
= 0.30,
P
< 0.001), low (
r
= -0.33,
P
< 0.001), and valgus implantations (
r
= 0.35,
P
< 0.001) of tibial components were related to shorter posterior KCDs.
Conclusion
Short posterior KCD after OUKA is a risk factor for postoperative tibial fracture. Patients with either malposition of the tibial component (too medial, low, and valgus) and/or a medial overhanging condyle exhibit a shorter distance of posterior KCD and higher rate of fracture.
Level of evidence:
Level III.
Purpose
The Simple Knee Value (SKV) is an outcome score in which patients are asked to grade their knee function as a percentage of that of a normal knee. The primary aim of this study was to ...validate the SKV by measuring its correlation with existing knee-related PROMs.
Methods
This was a prospective study conducted at a teaching hospital to assess the SKV’s validity. The study enrolled 47 young patients (16–54 years old), 49 older patients (≥ 55 years) and 30 healthy controls. A paper questionnaire consisting of the Lysholm, IKDC, KOOS, WOMAC and SKV was given to subjects three times (enrolment, 1-month preoperative visit and 6 months postoperative visit). The criterion validity of the SKV was determined by correlating it to existing knee PROMs using the Spearman correlation coefficient (S). SKV test–retest reliability was assessed by the intraclass correlation coefficient (ICC) between two time points (initial consultation at enrolment and preoperative visit, reflecting the same clinical condition). Responsiveness to change was determined by comparing the SKV scores before and after surgery (enrolment consultation and 6 months postoperative). Discriminative ability was determined by comparing the SKV distribution in patients and controls.
Results
There was a strong and significant correlation between the SKV and the gold standard Lysholm, IKDC, KOOS and WOMAC in the younger patients and the older patients (
p
< 0.0001). The reliability between the SKV at the initial consultation and before surgery was excellent (ICC 0.862, 95% CI 0.765; 0.921) in the younger patients, and moderate (ICC 0.506, 95% CI 0.265; 0.688) in the older patients. The SKV was responsive to change in both patient groups (
p
< 0.0001 for the SKV before versus 6 months after surgery). Like the other knee-specific PROMs (
p
< 0.0001), the SKV was able to distinguish between patients and controls (
p
< 0.0001).
Conclusions
The SKV is valid as it is significantly correlated to existing knee PROMs. It is also reliable, responsive to change and discriminating. Its simplicity gives it many advantages and it can be used by physicians in their daily practice.
Level of evidence
Level II.
Purpose
The primary aim of this study was to evaluate the phenotypic variation using the Coronal Plane Alignment of the Knee (CPAK) classification among 1000 knees with anteromedial osteoarthritis ...(OA) both prior to and following medial unicompartmental knee arthroplasty (UKA). The secondary aim of this study was to investigate whether knees maintained their preoperative CPAK phenotype and to evaluate the phenotypic alterations following medial UKA.
Methods
The CPAK classification was used to analyze 1000 knees that underwent medial UKA as treatment for anteromedial OA. Knees were categorized into nine distinct CPAK phenotypes based on their arithmetic hip–knee–ankle angle (aHKA), which estimates the pre-arthritic alignment, and joint line obliquity (JLO), both pre- and postoperatively. Phenotypic variation was analyzed by sex and age, and the phenotypic alterations following medial UKA were evaluated by phenotype.
Results
Preoperatively, CPAK phenotype I had the highest prevalence (45.0%). Among males, the preoperative prevalence of CPAK phenotype I was significantly higher compared to females (53.2% vs. 35.0%, respectively;
p
≤ .001), whereas females exhibited a significantly higher occurrence of CPAK phenotype V compared to males (9.8% vs. 4.4%, respectively;
p
≤ .015). Following medial UKA, CPAK phenotype II had the highest prevalence (53.3%). Overall, 45.1% of knees maintained their preoperative CPAK phenotype following medial UKA, which was most frequently observed among CPAK phenotype II (67.7%) and III (65.8%).
Conclusion
There is a substantial variation in CPAK phenotypes among knees with anteromedial OA, as well as following treatment with medial UKA. This variability challenges the assumption of uniform characteristics among knees with an identical wear pattern associated with anteromedial OA and emphasizes the complexity and variability of this specific form of OA.
Level of evidence
III, Retrospective cohort study.
Purpose
The aim of this study was to evaluate the anthropometric differences between knees of Indonesian Asians and Dutch Caucasians and the fit of nine different knee implant systems.
Methods
A ...total of 268 anteroposterior (AP) and lateral knee preoperative radiographs from 134 consecutive patients scheduled for total knee arthroplasty at two different centres in Jakarta and Leiden were included. Both patient groups were matched according to age and sex and included 67 Asians and 67 Caucasians. We assessed the radiographic differences between the Asian and Caucasian anthropometric data. The dimensions of the nine knee implant designs (Vanguard, Genesis II, Persona Standard, Persona Narrow, GK Sphere, Gemini, Attune Standard, Attune Narrow, and Sigma PFC) were compared with the patients’ anthropometric (distal femur and proximal tibia) measurements.
Results
The Dutch Caucasian patients had larger mediolateral (ML) and AP femoral and tibial dimensions than the Indonesian Asians. The aspect ratios of the distal femur and tibia were larger in Asians than in Caucasians. The AP and ML dimensions were mismatched between the tibial components of the nine knee systems and the Asian anthropometric data. Both groups had larger ML distal femoral dimensions than the knee systems.
Conclusion
Absolute and relative differences in knee dimensions exist not only between Asian and Caucasian knees but also within both groups. Not all TKA systems had a good fit with the Asian and Caucasian knee phenotypes. An increase in the range of available knee component sizes would be beneficial, although TKA remains an adequate compromise.
Level of evidence
III.
Background:
Previous research has found that the incidence of neurovascular injury is greatest among multiligamentous knee injuries (MLKIs) with documented knee dislocation (KD). However, it is ...unknown whether there is a comparative difference in functional recovery based on evidence of a true dislocation.
Purpose:
To determine whether the knee dislocation-3 (KD3) injury pattern of MLKI with documented tibiofemoral dislocation represents a more severe injury than KD3 MLKI without documented dislocation, as manifested by poorer clinical outcomes at long-term follow-up.
Study Design:
Cohort study; Level of evidence, 3.
Methods:
A multicenter retrospective cohort study was performed of patients who underwent surgical treatment for KD3 MLKI between May 2012 and February 2021. Outcomes were assessed using the International Knee Documentation Committee (IKDC) score, Lysholm score, Tegner activity scale, and visual analog scale (VAS) for pain. Documented dislocation was defined as a radiographically confirmed tibiofemoral disarticulation, the equivalent radiology report from outside transfer, or emergency department documentation of a knee reduction maneuver. Subgroup analysis was performed comparing lateral (KD3-L) versus medial (KD3-M) injuries. Multivariable linear regression was conducted to determine whether documented dislocation was predictive of outcomes.
Results:
A total of 42 patients (25 male, 17 female) were assessed at a mean 6.5-year follow-up (range, 2.1-10.7 years). Twenty patients (47.6%) were found to have a documented KD; they reported significantly lower IKDC (49.9 vs 63.0; P = .043), Lysholm (59.8 vs 74.5; P = .023), and Tegner activity level (2.9 vs 4.7; P = .027) scores than the patients without documented dislocation. VAS pain was not significantly different between groups (36.4 vs 33.5; P = .269). The incidence of neurovascular injury was greater among those with documented dislocation (45.0% vs 13.6%; P = .040). Subgroup analysis found that patients with KD3-L injuries experienced a greater deficit in Tegner activity level than patients with KD3-M injuries (Δ: –3.4 vs −1.2; P = .006) and had an increased incidence of neurovascular injury (41.7% vs 11.1%; P = .042). Documented dislocation status was predictive of poorer IKDC (β = −2.15; P = .038) and Lysholm (β = −2.85; P = .007) scores.
Conclusion:
Patients undergoing surgical management of KD3 injuries with true, documented KD had significantly worse clinical and functional outcomes than those with nondislocated joints at a mean 6.5-year follow-up. The current MLKI classification based solely on ligament involvement may be obscuring outcome research by not accounting for true dislocation.
A sizeable proportion of knee osteoarthritis is limited to the medial and patellofemoral compartments. Whilst short- and medium-term studies comparing bicompartmental knee arthroplasty (BCA) and ...total knee arthroplasty (TKA) have shown similar outcome scores, there are no studies comparing long-term outcomes. This study aims to determine which procedure resulted in superior long-term outcome scores.
Forty-eight patients with medial and patellofemoral compartment knee osteoarthritis were randomised to receive treatment in two groups: unlinked, modular BCA and TKA. The main outcome measures compared were the range of motion, Knee Society Function Score, Knee Society Knee Score, Oxford Knee Score, Physical Component Score and Mental Component Score of SF-36 pre-operatively and post-operatively up to 10 years. Radiographs of the operated knees were taken pre-operatively, post-operatively and at 10-year follow-up.
Twenty-six underwent BCA and 22 underwent TKA. Overall improvement was seen in both groups compared to pre-operatively, however there were no significant differences detected between the groups at 10 years. The median Hip–Knee–Ankle (HKA) angle was 183.38 (175.17–187.94) in the BCA group and 180.73 (174.96–185.65) in the TKA group. One patient from the BCA group had a peri-prosthetic fracture necessitating revision surgery to a TKA.
Outcome scores for BCA results were comparable to TKA at long-term follow-up. BCA is an alternative arthroplasty option in selected patients.
Purpose
Patient-specific instrumentation (PSI) is a technique to plan and position the prosthesis components in unicompartmental knee arthroplasty (UKA) surgery. This study assesses whether the ...definitive component position in the frontal, sagittal and axial plane is according to the preoperative plan, based on the hypothesis that PSI is accurate.
Methods
Twenty-six patients who had PSI Oxford UKA surgery were included prospectively. The component position in vivo was determined with a postoperative CT-scan and compared with the planned component position using MRI-based digital 3D imaging. Adjustments to the preoperative plan and implanted component sizes during surgery were recorded.
Results
Intraoperatively, no femoral adjustments were performed; 12 tibial re-resections were necessary. The median absolute deviation from the plan in degrees (range) in the frontal, sagittal and axial plane was 1.8° (− 1.5°–6.5°), 2.0° (− 6.5°–8.0°) and 1.0° (− 1.5°–5.0°) for the femoral component, and 2.5° (− 1.0°–6.0°), 3.0° (− 1.0°–5.0°) and 5.0° (− 6.5°–12.5°) for the tibial component. The femoral component is positioned 0.5 (− 1°–2.5°) mm more lateral and 0.8 (− 1.0°–2.5°) mm more anterior. The tibial component is positioned 2.0 (− 5.0–0.0) mm more lateral and 1.3 (− 3.0–6.0) mm more distal. The femoral and tibial default plans were changed four times (15.4%) and nine times (34.6%), respectively, before approval by the surgeon.
Conclusion
PSI in Oxford UKA surgery is reliable and accurately translates the preoperative plan into the in vivo situation, except for the tibial rotational position. The preoperative planning is a crucial step in avoiding re-resections that can cause angular deviations in prosthesis position, especially in tibial component rotational position. It is advised to avoid re-resections and to consider this while planning the PSI procedure.
Level of evidence
Prospective comparative study Level II.
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