Association of a Wider Medial Gap (Medial Laxity) in Flexion with Self-Reported Knee Instability After Medial-Pivot Total Knee Arthroplasty

Association Between Overhang of the Posterior Femoral Condyle and Restricted Postoperative Knee Flexion Related to Patient-Reported Stiffness in Medial-Pivot Total Knee Arthroplasty

BACKGROUND

The primary aim of this study was to investigate the association between the posterior longitudinal overhang in the femoral condyle (PLOF) in medial-pivot total knee arthroplasty (TKA) and a change in knee flexion angle (change in flexion).

METHODS

This retrospective cohort study included 148 knees undergoing medial-pivot TKA for medial knee osteoarthritis. The primary outcome was the change in flexion (c-flexion) preoperatively and 1 year postoperatively. The component positions were evaluated using three-dimensional measurements, where the PLOF was measured for each medial and lateral femoral condyle. The secondary outcome was the Western Ontario and McMaster Universities OA Index (WOMAC) scores taken preoperatively and 2 years postoperatively. A multivariate regression analysis was performed to determine predictors of c-flexion and risk factors for negative c-flexion (less than 0°). Furthermore, a receiver operating characteristic curve was utilized to determine the threshold for negative c-flexion.

RESULTS

The mean c-flexion was -3.2°± 8.7, and lateral PLOF was significantly associated with c-flexion (β = -0.52; P < 0.001). Larger preoperative flexion angles (odds ratio, 1.10; P <0.001) and larger lateral PLOF (odds ratio, 1.69; P = 0.001) were risk factors for negative c-flexion, with thresholds of 129° and 1.1 mm, respectively (sensitivity, 0.79; specificity, 0.72). Additionally, patients who had negative c-flexion (n = 91) demonstrated less improvement in preoperative and 2-year postoperative WOMAC stiffness subscores than patients who had positive c-flexion (0° or more; n = 57) (P = 0.01).

CONCLUSION

A larger lateral PLOF was associated with decreased and negative c-flexion after medial-pivot TKA. Patients who had negative c-flexion demonstrated less improvement in knee stiffness. Surgical strategies aimed at minimizing lateral PLOF may enhance postoperative knee flexion and overall patient outcomes in medial-pivot TKA.

Association of intraoperative medial joint gap laxity in the flexion position with subjective knee instability after fixed-bearing posterior-stabilised total knee arthroplasty

BACKGROUND

Postoperative subjective knee instability is an important clinical outcome after total knee arthroplasty (TKA), however the association with intraoperative soft tissue balance remains unclear. This study aimed to assess the association between intraoperative soft tissue balance and postoperative subjective knee instability in fixed-bearing posterior-stabilised (PS) TKA.

METHODS

This retrospective case-control study included 457 patients who underwent fixed-bearing PS TKA. Intra-articular distraction force was quantitatively applied to measure the gap parameters (length and angle) during surgery. The intraoperative joint gap parameters and postoperative clinical outcomes between the patients with (n = 90) and without (n = 367) subjective knee instability were compared. The risk factors for subjective postoperative knee instability were analysed using multivariate logistic regression analysis.

RESULTS

The patients with subjective knee instability demonstrated a medially wider intra-articular gap angle and worse Knee Society Score 2011 symptoms (18 vs. 21; p < 0.01), satisfaction (27 vs. 30; p < 0.01), functional activity (55 vs. 65; p < 0.01), and Forgotten Joint Score 12 items (51 vs. 65; p < 0.01) than those in the patients without subjective knee instability. The use of measured resection technique (odds ratio, 2.3; 95% CI, 1.1-4.8; p = 0.02) and the medial laxity of joint gap balance in the flexion position (odds ratio, 1.2; 95% CI, 1.0-1.4; p = 0.04) were detected as risk factors for postoperative subjective knee instability.

CONCLUSION

In fixed-bearing PS TKA, intraoperative medial joint laxity in the flexion position was associated with postoperative subjective knee instability, and surgical techniques to achieve sufficient soft tissue balance contributed to improve postoperative subjective clinical outcomes.

LEVEL OF EVIDENCE

Ⅲ (case-control study).

Intraoperative lateral laxity greater than 4° is associated with inferior functional improvement in posterior-stabilised total knee arthroplasty

PURPOSE

The study aimed to determine the impact of intraoperative lateral laxity at extension on clinical and functional outcomes 1 year after posterior-stabilised total knee arthroplasty (PS-TKA).

METHODS

In total, 91 varus-type osteoarthritic knees that underwent PS-TKA using the medial preservation gap technique were included. After the femoral trial component placement and patellofemoral joint reduction, the soft-tissue balance was assessed using an offset-type tensor with a 40-lb joint-distraction force. Patients were divided into the following three groups according to the intraoperative lateral laxity at extension (i.e., varus ligament balance) using the mean ± 1 standard deviation: Groups A, ≤0°; B, 0-4°; and C, >4°. The 2011 Knee Society Score (KSS) and 3-m timed up-and-go test (TUG) time 1-year postoperatively, and their improvements were compared among the groups.

RESULTS

While significant improvements were observed in all subscales of the 2011 KSS and TUG post-TKA (p < 0.05), the improvement of functional activities and TUG time were significantly lower in Group C than in Group B (p < 0.05). However, no significant differences were observed in symptom improvement, patient satisfaction or patient expectation scores among the groups.

CONCLUSION

An excessive lateral laxity (varus angle) >4° at extension was associated with lower improvement in functional ability 1-year postoperatively. Therefore, excessive intraoperative lateral laxity should be avoided in PS-TKA.

LEVEL OF EVIDENCE

Level IV.

Short-term functional outcomes of robotic-assisted TKA are better with functional alignment compared to adjusted mechanical alignment

INTRODUCTION

Ligament balancing is essential to the functional outcome of total knee arthroplasty (TKA). The optimal method of alignment remains a controversial issue. The primary objective was to compare the clinical outcomes of TKA between functional and adjusted mechanical alignment techniques. The secondary objectives were to compare bone resection, robotic alignment, and radiological assessment.

MATERIALS AND METHODS

This was a retrospective case-control series comparing TKA performed with functional alignment (FA) and adjusted mechanical alignment (aMA). Sixty-four FA subjects were matched with 64 aMA controls. These two groups were matched for age, gender, body mass index (BMI), surgeon, and type of frontal deformity. Both surgical procedures were performed using the MAKO® haptic robotic system. Functional scores (Forgotten Joint Score (FJS), Knee Society Score (KSS), and Oxford Knee Score (OKS)) were measured at the final postoperative follow-up. A radiographic evaluation was performed at the same time.

RESULTS

Mean FJS were respectively 63.4 ± 25.1 [0-100] and 51.2 ± 31.8 [0-100] in FA versus aMA group (p = 0.034). Mean OKS were respectively 40.8 ± 6.3 [21-48] and 34.9 ± 11.8 [3-48] in FA versus aMA group (p = 0.027). Mean KSS were respectively 184.9 ± 17.0 [126-200] and 175.6 ± 23.1 [102-200] in FA versus aMA group (p = 0.02). The main residual symptom was "none" for 73.0% versus 57.8%, "instability" for 6.4% versus 21.9%, "Pain" for 19.1% versus 12.5%, and "effusion" for 1.6% and 7.8% respectively for FA and aMA group (p = 0.016). There were 4 complications in the FA group versus 5 in the aMA group (p > 0.999). Mean postoperative hip-knee-ankle (HKA) robotic assessment were respectively 177.3° ± 2.0 [172-180] and 178.2° ± 2.0 [173-180] for FA and aMA group (p = 0.018). The median difference between HKA robotic and HKA radiological was -3.0° (IQR = 3.0; p < 0.001).

CONCLUSION

With greater residual deformity and without release, functional alignment showed a statistically significantly better short-term clinical outcome than adjusted mechanical alignment. This difference may not be clinically significant.

Varus/valgus stability in imageless robotic-assisted total knee arthroplasty applying three-dimensional assessment of varus/valgus stress X-rays

BACKGROUND

The postoperative varus/valgus stability assessment in stress X-rays has been established as an evaluation index. However, it is performed by the two-dimensional (2D) method rather than the three-dimensional (3D) method.

OBJECTIVE

This study aimed to identify the precision and reproducibility of measuring varus/valgus stress X-rays three-dimensionally and to examine varus/valgus stability under anesthesia in imageless robotic assisted total knee arthroplasty (rTKA).

METHODS

This prospective study analyzed 52 consecutive rTKAs (five males, 67 ± 5.3 years; 47 females, 74 ± 5.9 years). Postoperative varus/valgus stress X-rays in knee extension under anesthesia at manual maximum stress were three-dimensionally assessed by 2D-3D image matching technique using the 3D bone and component models. Varus/valgus angle between components (VV angle) in no stress, valgus stress, varus stress, medial joint opening (MJO), and lateral joint opening (LJO) were evaluated, clarifying this method's precision and reproducibility and valgus/varus stability.

RESULTS

All parameters' precision and reproducibility had <1° mean differences and high intra- and inter-class correlation coefficients. Bland-Altman plots showed no fixed and proportional bias. Non-stress VV angle, valgus VV angle, varus VV angle, MJO, and LJO were 3.6 ± 1.2°, 1.0 ± 1.4°, 7.1 ± 1.9°, 1.5 ± 1.0 mm, and 2.8 ± 2.7 mm, respectively.

CONCLUSION

This prospective study demonstrated that (1) the three-dimensional measurement method provided sufficient precision and reproducibility, and (2) the rTKAs could achieve good postoperative varus/valgus stability with a small standard deviation.

Lateral joint tightness in flexion following cementless mobile-bearing total knee arthroplasty decreases patient-reported outcome measures and postoperative range of motion

PURPOSE

The purpose of this study was to clarify the association between clinical outcomes and the flexion joint gap following rotating concave-convex (Vanguard ROCC) total knee arthroplasty (TKA).

METHODS

This consecutive retrospective series included 55 knees that underwent ROCC TKA. All the surgical procedures were performed using a spacer-based gap-balancing technique. To evaluate the medial and lateral flexion gaps, axial radiographs of the distal femur were obtained using the epicondylar view with a distraction force to the lower leg at 6 months postoperatively. Lateral joint tightness was defined as the lateral gap being greater than the medial gap. To evaluate clinical outcomes, patients were asked to complete patient-reported outcome measures (PROMs) questionnaires preoperatively and during at least 1 year of follow-up postoperatively.

RESULTS

The median follow-up duration was 24.0 months. Overall, 16.0% of patients had postoperative lateral joint tightness in flexion. The postoperative range of motion and PROMs were lower in patients with lateral joint tightness than in those with a balanced flexion gap or lateral joint laxity. No serious complications, including bearing dislocations, occurred during the observation period.

CONCLUSION

Lateral joint tightness in flexion following ROCC TKA decreases PROMs and postoperative range of motion.

LEVEL OF EVIDENCE: 4

Effect of mediolateral gap difference on postoperative outcomes in navigation-assisted total knee arthroplasty using an ultracongruent insert and the medial stabilising technique

PURPOSE

This study was aimed to compare the clinical, functional, and radiographic outcomes between symmetric and asymmetric extension and mediolateral gap balance after navigation-assisted (NA) total knee arthroplasty (TKA) using ultracongruent (UC) insets and the medial stabilising technique (MST).

METHODS

In all, 363 knees of 275 patients who underwent mechanical alignment-target NA TKA with MST between January 2015 and December 2017 were analysed. Patients were divided into balanced (extension mediolateral gap difference ≤ 2 mm) and tight medial (difference ≥ 3 mm) groups. Pre- and postoperative clinical, functional (range of motion, Western Ontario and McMaster University Osteoarthritis [WOMAC] index, Knee Society Knee Score [KSKS], and Knee Society Function Score [KSFS]) and radiographic (hip-knee-ankle [HKA] angle, femoral condylar offset, extension angle [a minus indicates hyperextension], and joint line distance) outcomes were compared between the groups. Student's t- or Chi-squared test was used to compare the outcomes.

RESULTS

Among the 363 knees analysed, 279 (77%) were assigned to the balanced group and 84 (23%) to the tight medial group. The preoperative HKA angle was significantly greater in the tight medial group than in the balanced group (9.7° ± 4.1° vs 14.3° ± 4.7°, P < 0.001). The postoperative WOMAC index, KSKS, and KSFS were similar between the groups. The change in the joint line distance was not significantly different (1.5 ± 3.7 vs 2.0 ± 3.3; n.s).

CONCLUSION

The clinical, functional, and radiographic outcomes, including joint line distance, were comparable between the tight medial and balanced group after mechanical alignment-targeted UC TKA with MST.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Navigated functional alignment total knee arthroplasty achieves reliable, reproducible and accurate results with high patient satisfaction

PURPOSE

The decision on which technique to perform a total knee arthroplasty (TKA) has become more complicated over the last decade. Perceived limitations of mechanical alignment (MA) and kinematic alignment (KA) have led to the development of the functional alignment (FA) philosophy. This study aims to report the 2-year results of an initial patient cohort in terms of revision rate, PROMs and complications for Computer Aided Surgery (CAS) Navigated FA TKA.

METHODS

This paper reports a single surgeon's outcomes of 165 consecutive CAS FA TKAs. The final follow-up was 24 months. Pre-operative and post-operative patient-reported outcome measures, WOMAC and KSS, and intra-operative CAS data, including alignment, kinematic curves, and gaps, are reported. Stress kinematic curves were analysed for correlation with CAS final alignment and CAS final alignment with radiographic long-leg alignment. Pre- and post-operative CPAK and knee phenotypes were recorded. Three different types of prostheses from two manufacturers were used, and outcomes were compared. Soft tissue releases, revision and complication data are also reported.

RESULTS

Mean pre-operative WOMAC was 48.8 and 1.2 at the time of the final follow-up. KSS was 48.8 and 93.7, respectively. Pre- and post-operative range of motion was 118.6° and 120.1°, respectively. Pre-operative and final kinematic curve prediction had an accuracy of 91.8%. CAS data pre-operative stress alignment and final alignment strongly correlate in extension and flexion, r = 0.926 and 0.856, p < 0.001. No statistical outcome difference was detected between the types of prostheses. 14.5% of patients required soft tissue release, with the lateral release (50%) and posterior capsule (29%) being the most common.

CONCLUSION

CAS FA TKA in this cohort proved to be a predictable, reliable, and reproducible technique with acceptable short-term revision rates and high PROMs. FA can account for extremes in individual patient bony morphology and achieve desired gap and kinematic targets with soft tissue releases required in only 14.5% of patients.

LEVEL OF EVIDENCE

IV (retrospective case series review).

Does diabetes mellitus impair the clinical results of total knee arthroplasty under enhanced recovery after surgery?

BACKGROUND

Diabetes mellitus (DM) and osteoarthritis (OA) are common diseases that are predicted to increase in prevalence, and DM is a risk factor for OA progression and has a negative impact on the outcome. However, the evidence remains unclear on how it affects patients' clinical results of total knee arthroplasty (TKA) under enhanced recovery after surgery (ERAS).

METHODS

A retrospective single-center study was conducted comparing diabetic and non-diabetic patients who underwent TKA in West China Hospital of Sichuan University between September 2016 to December 2017 under ERAS. Consecutive propensity score matching (PSM) was conducted by 1:1 (DM: non-DM) matching analysis with all baselines as covariates. The primary clinical results were the improvement of knee joint function, the incidence of postoperative complications, and the FJS-12 sensory results 5 years after the operation between DM and Non-DM groups. The secondary clinical results were the postoperative length of stay (LOS), postoperative blood test and total blood loss (TBL).

RESULT

After PSM, the final analysis included 84 diabetic patients and 84 non-diabetic patients. Diabetic patients were more likely to experience early postoperative complications (21.4% vs. 4.8%, P = 0.003), of which wound complications are the most significant (10.7% vs. 1.2%, P = 0.022). Diabetic patients experienced longer postoperative LOS with a significant increase in patients with LOS exceeding 3 days (66.7% vs. 50%, P = 0.028) and showed less postoperative range of motion (ROM) (106.43 ± 7.88 vs. 109.50 ± 6.33 degrees, P = 0. 011). Diabetic patients also reported lower Forgotten joint score (FJS-12) than non-diabetic patients (68.16 + 12.16 vs. 71.57 + 10.75, P = 0.020) in the 5-year follow-up and were less likely to achieve a forgotten knee joint (10.7% vs. 1.2%, P = 0.022). In additional, Compared with non-diabetics, diabetic patients showed lower hemoglobin (Hb) (P < 0.001) and hematocrit (HCT) (P < 0.001) and were more likely to suffer from hypertension before TKA (P < 0.001).

CONCLUSION

Diabetic patients show increased risk for postoperative complications, and have lower lower postoperative ROM and lower FJS-12 compared with non-diabetic patients after TKA under ERAS. More perioperative protocols are still needed to be investigated and optimized for diabetic patients.

Joint gap produced by manual stress is dependent on the surgeon's experience and is smaller in flexion in robotic-assisted total knee arthroplasty

PURPOSE

This study aimed to retrospectively investigate (1) the reproducibility of gap measurements by manual stress using the Z-shaped retractor depending on the surgeon's experience with this maneuver and (2) the consistency of the gap distraction force produced by manual stress throughout the range of motion (ROM) in the robotic-assisted total knee arthroplasty (TKA). It was hypothesized that the joint gap produced by manual stress is not reproducible depending on the surgeon's experience, and the distraction force applied by manual stress throughout the ROM is not constant.

METHODS

Medial and lateral joint gaps were obtained throughout the ROM by manual stress or a tensioner by two surgeons with different levels of experience in robotic-assisted TKA. The association between the differences in gap measurement by the two surgeons and the preoperative radiographic parameters, including the hip-knee-ankle (HKA) angle and absolute and relative varus/valgus laxities were analyzed.

RESULTS

The experienced surgeon produced significantly greater gaps than the inexperienced surgeon from 0° to 100° flexion, with a mean difference of 0.35 ± 0.12 mm in the medial gap (p < 0.0001), and from 10° to 120° flexion with a mean difference of 0.57 ± 0.13 mm in the lateral gap (p < 0.0001). The tensioner produced a significantly greater medial gap from 70° to 110° flexion with a mean difference of 0.32 ± 0.01 mm in the medial gap (p < 0.0001) and from 0° to 110° flexion with a mean difference of 1.12 ± 0.26 mm in the lateral gap (p < 0.0001). The differences in gap distance by manual stress between experienced and inexperienced surgeons were moderately correlated with the HKA angle in the lateral gap (r = 0.40, p = 0.01). The gap differences due to manual stress and a tensioner showed moderate negative correlation with the HKA angle in the medial gap (r = - 0.50, p = 0.001) and weak negative correlation with the absolute valgus laxity in the lateral gap (r = - 0.35, p = 0.03).

CONCLUSIONS

The joint distraction force by manual stress may differ depending on the surgeon's experience and tended to be smaller in deep flexion; therefore, the flexion gap may be underestimated. Surgeons should determine implant positioning considering gap balance by manual stress, taking into account these characteristics of the manual stress maneuver.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.