Enlarged post-operative posterior condyle tightens extension gap in total knee arthroplasty

Addressing sagittal plane imbalance in primary total knee arthroplasty

Aims

Sagittal plane imbalance (SPI), or asymmetry between extension and flexion gaps, is an important issue in total knee arthroplasty (TKA). The purpose of this study was to compare SPI between kinematic alignment (KA), mechanical alignment (MA), and functional alignment (FA) strategies.

Methods

In 137 robotic-assisted TKAs, extension and flexion stressed gap laxities and bone resections were measured. The primary outcome was the proportion and magnitude of medial and lateral SPI (gap differential > 2.0 mm) for KA, MA, and FA. Secondary outcomes were the proportion of knees with severe (> 4.0 mm) SPI, and resection thicknesses for each technique, with KA as reference.

Results

FA showed significantly lower rates of medial and lateral SPI (2.9% and 2.2%) compared to KA (45.3%; p < 0.001, and 25.5%; p < 0.001) and compared to MA (52.6%; p < 0.001 and 29.9%; p < 0.001). There was no difference in medial and lateral SPI between KA and MA (p = 0.228 and p = 0.417, respectively). FA showed significantly lower rates of severe medial and lateral SPI (0 and 0%) compared to KA (8.0%; p < 0.001 and 7.3%; p = 0.001) and compared to MA (10.2%; p < 0.001 and 4.4%; p = 0.013). There was no difference in severe medial and lateral SPI between KA and MA (p = 0.527 and p = 0.307, respectively). MA resulted in thinner resections than KA in medial extension (mean difference (MD) 1.4 mm, SD 1.9; p < 0.001), medial flexion (MD 1.5 mm, SD 1.8; p < 0.001), and lateral extension (MD 1.1 mm, SD 1.9; p < 0.001). FA resulted in thinner resections than KA in medial extension (MD 1.6 mm, SD 1.4; p < 0.001) and lateral extension (MD 2.0 mm, SD 1.6; p < 0.001), but in thicker medial flexion resections (MD 0.8 mm, SD 1.4; p < 0.001).

Conclusion

Mechanical and kinematic alignment (measured resection techniques) result in high rates of SPI. Pre-resection angular and translational adjustments with functional alignment, with typically smaller distal than posterior femoral resection, address this issue.

A Three-dimensional Comparison of Pre- and Post-component Position in a Series of Off-label Robotic-assisted Revision Total Knee Arthroplasties

Background

The application of robotic-assisted arthroplasty in revision knee scenarios continues to evolve. This study compares the pre- and post-revision implant positions in series of revision total knee arthroplasties (TKA) using a robotic arm system.

Methods

Twenty-five consecutive off-label robotic-assisted revision TKA were performed. After virtual revision femoral and tibial components were positioned to achieve "balanced" medial and lateral flexion and extension gaps, the existing primary implants (PI) were removed, and bone cuts were executed with the robotic arm system. Preoperative coronal, sagittal, and axial position of the PI was compared to the final planned positions of the robotic revision implants (RRI) for each subject. A repeated measures ANOVA using the absolute difference in millimeters and degrees between the PI and RRI orientation was completed.

Results

Intra-operatively, the virtual gaps were balanced within the planning software followed by successful execution of the plan. There was a statistically significant difference between posterior condylar offset and tibial component positioning for RRI compared to PI. There was no difference between the distal femoral component values between PI and RRI.

Conclusions

The sagittal alignment of the revision implants, specifically the femoral posterior condylar offset and tibial component slope, are statistically significant considerations for a stable revision TKA with off-label use of a robotic-arm system. Other potential benefits may include appropriate implant sizing which can affect the resultant ligamentous tension important for a functional revision TKA. Future research and software iterations will be needed to determine the overall accuracy and utility of robotic-assisted revision TKA.

The clinical results of bi-cruciate vs posterior stabilized total knee arthroplasty for flexion contracture in osteoarthritic knee

BACKGROUND

The improvement of flexion contracture is important in knee arthroplasty since residual flexion contracture postoperatively is associated with decreased quality of life and patient satisfaction. In this study, we investigated the effect of bi-cruciate stabilized (BCS)-type total knee arthroplasty (TKA) as compared to posterior stabilized (PS)-type TKA on osteoarthritic primary knees with flexion contractures.

METHODS

59 TKAs from January 2014 to December 2020, of which 30 were PS-type TKAs (NexGen LPS-flexⓇ; 76.3 years, BMI 27.5) and 29 BCS-type TKAs (Journey IIⓇ; 72.5 years, BMI 28.6), were performed for knee osteoarthritis with preoperative flexion contracture of 15° or greater. Full extension was obtained intraoperatively during all TKAs. Clinical outcomes, radiological evaluations, and the amount of additional distal femoral osteotomy during TKA were evaluated in a retrospective study design.

RESULTS

The range of motion improved in the both groups. Postoperative flexion contracture was significantly improved in the BCS group. Knee Society Score improved significantly in both groups, with no difference between the two groups. The amount of additional distal femoral osteotomy was 2.5 ± 1.3 mm for the PS group, and 1.8 ± 1.5 mm for the BCS group, showing a significant difference (p = 0.04).

DISCUSSION

The BCS-type TKA significantly improved preoperative flexion contracture and reduced the amount of additional distal femoral osteotomy compared to PS-type TKA. This is attributed to the anterior cam in the BCS-type TKA, which leads to a smaller amount of protrusion of the posterior femoral condyle from the posterior margin of the tibial component in the BCS-type in knee extension, as compared to the PS-type.

Risk factors of de novo hyperextension developed after posterior cruciate ligament substituting total knee arthroplasty: a matched case-control study

PURPOSE

To investigate factors contributing to the de novo hyperextension after posterior cruciate ligament substituting (PS) total knee arthroplasty (TKA).

METHODS

Through a retrospective case-control study, de novo hyperextension patients were compared with patients without hyperextension after primary PS TKA. Eighty-five hyperextension patients were compared with 85 patients in a control group matched by age, sex, surgeon and implant. The clinical and radiographic parameters, including the mechanical axis (MA), joint line convergence angle (JLCA), posterior tibial slope angle (PTSA), posterior condylar offset (PCO), and the gamma angle, were evaluated preoperatively and immediate postoperatively. Comparisons between the two groups and logistic regression analysis were performed to investigate factors contributing to de novo hyperextension.

RESULTS

Among the clinical factors, preoperative flexion contracture was less (5° ± 6° vs. 11° ± 6°, p < 0.001) and the range of motion was greater (125° ± 12° vs. 118° ± 5°, p = 0.041) in the de novo hyperextension group than in the control group. Among the radiographic parameters, preoperative and postoperative JLCA were greater (8.1° ± 4.4° vs. 6.1° ± 3.5°, p < 0.001, 1.0° ± 1.3° vs. 0.2° ± 0.8°, p = 0.002, respectively), postoperative PTSA was greater (3.7° ± 2.0° vs. 3.3° ± 1.6°, p < 0.001) and preoperative and postoperative PCO were less in the hyperextension group than in the control group (26.3 mm ± 3.3 mm vs. 29.1 mm ± 3.2 mm, p < 0.001, 26.4 mm ± 3.2 mm vs. 29.1 mm ± 3.0 mm, p < 0.001, respectively), whereas, change in PCO was greater in the hyperextension group (1.1 mm ± 7.7 mm vs. - 0.1 mm ± 3.3 mm, p < 0.001). In multivariate analysis, the degree of medial soft tissue release [odds ratio (OR) 2.83, p = 0.003], flexion contracture [OR 0.86, p = 0.028], postoperative JLCA [OR 2.45, p = 0.004], preoperative PCO and a change in PCO [OR 0.74, p = 0.002, OR 1.89, p = 0.001, respectively] were the factors associated with de novo hyperextension.

CONCLUSIONS

An increased degree of medial soft tissue release, small preoperative flexion contracture, increased postoperative JLCA, decreased preoperative PCO and increased change in PCO were risk factors of de novo hyperextension.

LEVEL OF EVIDENCE

III.

Intraoperative changes in medial joint gap after posterior femoral condylar resection, posterior osteophyte removal, and femoral component placement during primary total knee arthroplasty

BACKGROUND

"Mid-flexion stability" is important for superior patient satisfaction following total knee arthroplasty (TKA). Thus, it is important to control medial joint gap intraoperatively as a countermeasure. However, reports on the precise intraoperative changes in medial joint gap during TKA are scarce. This study evaluated the intraoperative changes in medial joint gap during TKA.

METHODS

We studied 167 knees with varus osteoarthritis that underwent 80 cruciate-retaining (CR) and 87 posterior-stabilized (PS) TKAs between January 2018 and December 2020. We measured the intraoperative changes in medial joint gap with a tensor device at 137.5 N.

RESULTS

The medial joint gap after posterior femoral condylar resection was significantly increased not only at 90° of flexion but also at 0° of extension in CR and PS TKAs (p < 0.01). The medial joint gap after posterior osteophyte removal was significantly increased not only at 0° of extension but also at 90° of flexion in CR and PS TKAs (p < 0.01). The medial joint gap at 0° of extension was reduced by 0.60 mm after femoral component placement in PS TKA.

CONCLUSION

Surgeons need to pay close attention to these intraoperative changes in medial joint gap by measuring the medial joint gap before and after each procedure or assuming the changes in those values before bone cutting to achieve superior patient satisfaction following TKA.

Posteromedial Compartment Arthroscopy of the Knee and Resection of Osteophytes: An Anatomic Perspective on Posteromedial Knee Impingement

Posteromedial knee pain is a common clinical problem. It is often accompanied by degenerative changes or tears in the posterior horn of the medial meniscus and/or pain during deep flexion of the knee. In more advanced cases, it is accompanied by the osteophytic formation of a cam lesion that develops gradually in the posterior of the medial condyle of the femur and, with it (or less frequently without it), an osteophytic lesion at the posterior of the tibia (i.e. pincer lesion) occurs. It is believed that resection of the cam lesion may delay the progression of knee osteoarthritis, similarly to repairing the posterior horn of the medial meniscus. In this technical note, we describe a 2-portal technique for resection of cam lesions by posteromedial knee arthroscopy using anatomic landmarks. Using both portals provides better visualization and a better approach.

Optimal intraoperative medial joint gap in extension to prevent flexion contracture following total knee arthroplasty using modified gap balancing technique

Background

Primary aim to identify the ideal medial joint gap in extension needed to prevent post-operative flexion contracture following total knee arthroplasty (TKA) in varus osteoarthritic knees by the modified gap balancing technique. A secondary aim was to analyze multiple factors that influence knee extension in TKA by modified gap balancing.

Methods

This is a prospective cohort study of 150 patients diagnosed with osteoarthritic varus knee who underwent TKA using the modified gap balancing technique. Operative and clinical records were assessed to determine factors including age, BMI (Body mass index), pre-operative extension angle and the medial extension laxity. Patients were followed for 6-months post-operatively and reviewed for knee extension angle.

Results

Six months final follow-up information was available for 148 patients with an average age of 75.5 years. Pre-operative knee extension and BMI were significantly associated with post-operative knee extension. Post-operative flexion contracture of ≧ 100 was not seen in any of 34 patients with a medial extension laxity ≧ 0 mm who had no pre-existing flexion contracture, and in 1/9 (11.1%) patients with a medial extension laxity ≧ 1 mm who had pre-existing flexion contracture.

Conclusions

Pre-operative extension angle and BMI significantly influence the post-operative knee extension angle in TKA using the modified gap balancing technique. A medial extension laxity of at least 1 mm is ideally needed to prevent post-operative flexion contracture in patients with a pre-existing contracture ≧ 100.

Level of evidence

Level II; Prospective cohort study.

The knee position at tourniquet inflation does not affect the gap balancing during total knee arthroplasty

INTRODUCTION

The relationship between gap balancing and clinical outcome of total knee arthroplasty (TKA) has been researched. Tourniquet is widely used by most surgeons; however, there are little quantitative data about the gap depending on the tourniquet usage. We aimed to investigate whether the knee position at tourniquet inflation affected the gap measurement intra-operatively.

METHODS

TKA was performed for 104 knees and the tourniquet was inflated with the knee at full flexion and extension. The gap was measured in each static knee flexion status (0°, 30°, 45°, 60°, 90°, 120°, and in full flexion) using a tensor. We measured the gap twice; under the tourniquet inflation and release. The gap difference at each static knee flexion status was calculated by subtracting the gap under release from that under inflation.

RESULTS

When the tourniquet was inflated with the knee at full flexion, the mean gap differences were < 1 mm and < 1° in each static knee flexion status. When the tourniquet was inflated with the knee at full extension, the mean gap differences were < 1 mm and < 1°, respectively. All values of the gap difference were minimum, and were not affected by the tourniquet, whether the knee position at the tourniquet inflation was flexed or extended.

CONCLUSIONS

We postulated that the knee position at tourniquet inflation would affect the gap, which was refuted by our results. This shows that we can measure the gap without considering the knee position at tourniquet inflation.

Decreasing Posterior Femoral Condyle Offset Improves Intraoperative Correction of Flexion Contracture in Total Knee Arthroplasty

Multiple intraoperative strategies are described to achieve full extension in total knee arthroplasty, but only a few studies have assessed the effect of the flexion gap on intraoperative improvement in flexion contracture. The aim of this study was to determine whether posterior condylar offset, in isolation, independently affects extension at the time of total knee arthroplasty.Two hundred and seventy-eight patients who underwent total knee arthroplasty for knee osteoarthritis and flexion contracture ≥ 5 degrees between January 2008 and July 2018 were included in this study. Patients with other factors that could affect knee extension at the time of surgery were excluded. We recorded the thickness of posterior femoral condyle bone resected as well as the thickness of the posterior femoral component chosen for each patient. Patients' knee extension was recorded under anesthetic, prior to resection and intraoperatively after total knee replacement.Average thickness of bone resection for the posteromedial femur was 12.64  ± 1.65 mm and for the posterolateral femur was 10.38  ± 1.52 mm. Using a linear regression model, we found that changes in posterior offset and implant downsizing influenced correction of fixed flexion deformity at the time of surgery. When patients had a combined posteromedial and posterolateral offset 2 mm thinner than the thickness of bone resected, there was an average correction of 3.5 degrees of flexion contracture.Our study demonstrated that posterior femoral condyle offset is an independent variable affecting correction of flexion contracture at the time of surgery in a gap balanced cruciate-retaining total knee arthroplasty. This is a level IV evidence study.

Biomechanical Effect of Coronal Alignment and Ligament Laxity in Total Knee Arthroplasty: A Simulation Study

The purposes of this study were to develop a cruciate-retaining total knee arthroplasty musculoskeletal model, which enables the adjustment of ligament length and implant alignment; validate the model; and evaluate the effects of varus/valgus alignment adjustment and unbalanced medial/lateral ligament laxity during gait. A cruciate-retaining total knee arthroplasty musculoskeletal model was constructed and validated against the in vivo contact forces. This model was transformed to 2° varus/valgus alignment of femoral or tibial replacement models and 2° medial/lateral laxity models. The contact forces and ligament tensions of the adjusted models were calculated. The contact forces in the model showed good agreement with the in vivo contact forces. Valgus replacement alignment with balanced ligament models showed a lower contact force at the medial compartment than at the neutral alignment model, whereas the varus replacement alignment with balanced ligament models showed a greater contact force at the medial compartment and medial/posterior cruciate ligament tension. The medial laxity with neutral alignment model showed a similar contact force with decreased medial ligament tension compared to the balanced neutral alignment model, whereas the lateral laxity with the neutral alignment model showed a greater contact force and decreased lateral ligament tension. The cruciate-retaining total knee arthroplasty model was validated using in vivo contact forces (r = 0.939) Two degrees of valgus alignment adjustment with balanced ligament or neutral alignment with 2° of medial laxity can be safe without increasing contact force or ligament tension compared to neutral alignment with a balanced extension gap. However, 2° of varus alignment adjustment with balanced ligament or neutral alignment with 2° of lateral laxity may be unfavorable due to the overloading of the joints and knee ligaments.

Component gap measurement reflects the planned gap balance during total knee arthroplasty more accurately and reliably than bone surface gap measurement

PURPOSE

This study aimed to compare the reliability of two gap assessment methods (component and bone surface gap measurement vs. planned gap balance) and identify the contributors to component gaps other than planned gaps.

METHODS

The prospectively collected data for 122 consecutive primary total knee arthroplasties (TKAs; 114 patients). After femoral planning for gap balancing, the medial and lateral planned gaps were calculated (planned gap). The established medial extension and flexion gaps (MEG and MFG, respectively) and lateral extension and flexion gaps (LEG and LFG, respectively) were measured with and without the TKA components (bone surface and component gaps) at 0° and 90° flexion. The intraclass and Pearson correlation coefficients for each gap measurement method were assessed using planned gap values, and multiple linear regression analyses were performed to identify the contributors to component gaps.

RESULTS

Compared with the bone surface gap measurement, the component gap measurement showed higher reliability and stronger correlation with the planned gap balance for each gap. The changes in the medial posterior femoral offset contributed to the MEG and LEG, whereas those in the joint line height contributed to the LEG. The changes in the hip-knee-ankle angle and lateral posterior femoral offset contributed to the LFG.

CONCLUSION

Component gap measurements of the established gap more accurately and reliably reflect the planned gap balance than do bone surface gap measurements. The established gaps are affected by several factors other than femoral planning.

The role of joint line position and restoration of posterior condylar offset in revision total knee arthroplasty : a systematic review of 422 revision knees arthroplasty

The aim of this systematic review was to evaluate the evidence on reservation of Posterior Femoral Condylar Offset (PFCO) and Joint Line (JL) after Revision Total Knee Arthroplasty (RTKA) for im- proved functional outcomes. A comprehensive search of PubMed, Medline, Cochrane, CINAHL, and Embase databases was conducted, with papers published from the inception of the database to October 2020 included. All relevant articles were retrieved, and their bibliographies were hand searched for further references on Posterior condylar offset and revision total knee arthroplasty. The search strategy yielded 28 articles. After duplicate titles were excluded, abstracts and full text were reviewed. Nine studies were assessed for eligibility, four studies were excluded because they did not fully comply with the inclusion criteria. Six articles were finally included in this systematic review. Based on this systematic review restoration of the JL and PFCO in RTKR is associated with a significant improvement in the post-operative range of motion, KSS, OKS, patellar function, and SF-36. Reservation of JL should be a major consideration when undertaking RTKA. Of note, increasing PFCO to balance the flexion gap while maintaining joint line should be well assessed intra-operatively. The upper limit of the PFCO that widely accepted is up to 40 % greater than that of the native knee. 4 mm is the upper limit for JL restoration. Level of evidence III.

What is the Effect of Posterior Osteophytes on Flexion and Extension Gaps in Total Knee Arthroplasty? A Cadaveric Study

Background

Posterior compartment knee osteophytes may pose a challenge in achieving soft-tissue balance during total knee arthroplasty (TKA). Obtaining symmetry of flexion and extension gaps involves balance of both bony and soft-tissue structures. We hypothesize that space-occupying posteromedial femoral osteophytes affect soft-tissue balance.

Methods

Five cadaveric limbs were acquired. Computed tomography scans were obtained to define the osseous contours. Three-dimensionally printed, specimen-specific synthetic posterior femoral osteophytes were fabricated in 10-mm and 15-mm sizes. TKAs were implanted. Medial and lateral compartment contact forces were measured during passive knee motion using pressure-sensing technology. For each specimen, trials were completed without osteophytes and with 10-mm and 15-mm osteophytes affixed to the posteromedial femoral condyle. Contact forces were obtained at full extension, 10°, 30°, 45°, 60°, and 90° of flexion. These were recorded across each specimen in each condition for three trials. Tukey post hoc tests were used with a repeated measures ANOVA for statistical data analysis.

Results

The presence of posteromedial osteophytes increased asymmetric loading from full extension to 45° of flexion, with statistically significant differences observed at full extension and 30°. A reduction in lateral compartment forces was noted. The 25%-75% bounds of variability in the contact force was less than 3.5 lbs.

Conclusions

Posteromedial femoral osteophytes caused an asymmetric increase in medial contact forces from full extension continuing into mid-flexion. The soft-tissue imbalance created from these osteophytes supports their removal before performing ligament releases to obtain desired soft-tissue balancing during TKA.

Posterior tibial slope is a modifiable predictor of relatively large extension gaps in total knee arthroplasty for degenerative osteoarthritis

BACKGROUND

During total knee arthroplasty (TKA) for osteoarthritis, the sagittal gap imbalance (SGI) with a relatively large extension gap is an important surgical challenge. We determined the predictors of SGI with a relatively large extension gap and evaluated the surgical outcomes of knees with SGI.

METHODS

551 consecutive cases of primary TKA for osteoarthritis were retrospectively reviewed. The cohort was divided into two groups according to the SGI and statistically matched according to baseline characteristics via the inverse probability of treatment weighting method. Multiple linear and logistic regression analyses were performed to determine the predictors of sagittal gap difference (SGD) and SGI. Intergroup differences in clinical and radiological outcomes were analyzed.

RESULTS

Of all the knees included, 8.5% (n = 45) presented with SGI with a relatively large extension gap and required femoral sagittal balancing to manage SGI. The hyperextension angle (HA), preoperative joint line convergence angle (JLCA), and the change in posterior tibial slope (PTS) significantly correlated to SGD and predicted SGI with a relatively large extension gap. SGI group showed significant changes in femoral posterior condylar offset and joint line height compared to those without SGI (1.48 vs -0.45, 1.37 vs -0.51, respectively). Postoperative ROM and knee society knee scores were lower in SGI group.

CONCLUSION

Knees requiring sagittal balancing to manage SGI with a relatively large extension gap is not uncommon in TKA for osteoarthritic knees. The change in PTS is an independent and modifiable predictor of SGI.

Is it possible to predict the final component gap in flexion before femoral posterior condylar osteotomy in cruciate-retaining and posterior-stabilized total knee arthroplasty?

BACKGROUND

In total knee arthroplasty (TKA) with posterior condylar osteotomy using anatomical landmarks, predicting the final flexion gap is impossible, as it differs with the presence or absence of the posterior cruciate ligament. We compared the predicted flexion gap, based on pre-femoral posterior condylar osteotomy measurements, with the postsurgical final flexion gap in cruciate-retaining (CR) and posterior-stabilized (PS) TKA.

METHODS

One hundred knees of patients with osteoarthritis were included: 35 underwent CR, and 65 PS TKA. Distal femoral and proximal tibial osteotomy using the measured resection technique was performed. An anterior and posterior femoral osteotomy guide was set parallel to the surgical epicondylar axis, and the predicted flexion gap was measured using a seesaw tensor attached to the guide. After all procedures, the final component gap in flexion was measured using a similar seesaw tensor at the patella reduction position and was compared with the predicted gap.

RESULTS

The correlation coefficients for predicted vs. final component gap were 0.45 (P < 0.05) in CR and 0.82 (P < 0.001) in PS. The mean differences between predicted and final gaps were 1.8 mm for CR and 1.0 mm for PS. In 34.3% of CR cases, the gap difference was more than 2 mm.

CONCLUSION

It is possible to predict the final flexion gap before femoral posterior condylar osteotomy, with a strong correlation observed between predicted and final component gaps in PS TKA. However, in CR, more than 30% of the cases showed unexpectedly large final flexion gaps.

Intraoperative manipulation for flexion contracture during total knee arthroplasty

BACKGROUND

Joint gap unbalancing during total knee arthroplasty (TKA) induces flexion contracture. Flexion contracture is one of the most serious complications of TKA. When flexion contracture is found during surgery, intraoperative manipulation is often empirically performed. We evaluated the effects of intraoperative manipulation on joint gap and postoperative flexion contracture.

MATERIALS AND METHODS

TKA was performed for 136 knees. Intraoperative manipulation was performed for flexion contracture in 61 knees. Joint gap changes before and after manipulation were measured at six positions from extension to 120° of flexion. Manipulation was not performed for 75 knees. The extension angle was measured radiographically immediately after surgery, at 3 months, and 6 months postoperatively. Extension angles with manipulation and without manipulation were compared.

RESULTS

Joint gap changes (mm) before and after manipulation were 0.1, 0.0, -0.2, -0.3, -0.1, and -0.3 at 0°, 30°, 45°, 60°, 90°, and 120° of flexion, respectively, indicating that manipulation could not change joint gaps significantly. Extension angles (°) with and without manipulation were -4.0 ± 4.6 and -3.8 ± 3.9 immediately after surgery, -5.3 ± 6.7 and -5.5 ± 6.2 at 3 months postoperatively, and -2.7 ± 6.0 and -3.8 ± 5.8 at 6 months postoperatively. No statistically significant difference existed between the values with or without manipulation during all periods.

CONCLUSION

Intraoperative manipulation does not enlarge the gap or resolve postoperative flexion contracture. Developing the new surgical technique is required to achieve perfect balance at TKA.

Large osteophyte removal from the posterior femoral condyle significantly improves extension at the time of surgery in a total knee arthroplasty

Removing osteophytes from the posterior compartment of the femur eliminates the tenting effects on the joint capsule and consequently increases the extension gap in total knee arthroplasty. However, there is no clear association with the size of osteophytes removed and the potential degree of additional extension achieved at time of surgery.

Aims

Correlate the size of posterior osteophytes removed with the degree of extension gained intraoperatively in total knee arthroplasty and develop a radiological classification system to grade these osteophytes.

Methods

Patients who underwent a TKA had pre and post operative sagittal radiographs assessed and classified according to 4 different categories of a proposed classification system. Knee extension was then assessed by a computer navigated system before incision and after implant insertion. Confounding factors were controlled and considered on the analysis. The study was done retrospectively.

Results

147 patients were included in the study. Ninety-three (63.2%) patients had osteophytes on the posterior aspect of the femur completely removed and fifty-four patients (36.8%) did not have radiological evidence of osteophytes on the posterior aspect of the femur. There was a positive and linear correlation (Pearson correlation 0.327, p .005) between osteophyte size and degree of extension corrected at time of surgery. On Multivariate Logistic Regression Analysis, we found that small osteophytes (Grade 1) did not seem to affect the extension, while removing Grade 2 or Grade 3 osteophytes lead to a gain in extension of 2.7 and 4.5° respectively.

Conclusion

Removing large osteophytes (Grade 2 and Grade 3) from the posterior femoral compartment can be used as an adjuvant strategy to ensure that intraoperative extension is optimal. However removing small osteophytes (Grade 1) should not be expected to affect extension at the time of surgery in TKA and could increase intra-operative time and morbidity.

Risk factors of hyperextension and its relationship with the clinical outcomes following mobile-bearing total knee arthroplasty

INTRODUCTION

To evaluate the incidence and risk factors of postoperative hyperextension after mobile-bearing total knee arthroplasty (TKA) and its clinical outcomes.

MATERIALS AND METHODS

This retrospective case-control study included 387 knees of primary TKA patients after a 5-year follow-up. The clinical outcomes and radiographs including posterior condylar offset (PCO), femur and tibial slope angle and its discrepancy were evaluated. The patients were divided into two groups (group 1: non-hyperextension, group 2: hyperextension). An extension greater than 5° measured using a goniometer at the final follow-up was defined as hyperextension. Logistic and linear regression analyses were performed.

RESULTS

Overall, 43 knees (11.1%) with hyperextension were observed at the last follow-up. There was no significant difference between groups in terms of the clinical outcomes although the functional scores were worse in group 2. There was no significant difference in the postoperative radiologic evaluation except for a change in PCO (group 1 vs. group 2; - 0.2 mm ± 3.8 vs. - 2.4 mm ± 3.0, p = 0.003), distal femoral resection slope angle (- 9.1° ± 2.1 vs. - 12.1° ± 1.7, p < 0.000) and discrepancy of the slope angle (0.3° ± 4.5 vs. - 3.6° ± 3.9, p < 0.000). The change in PCO [odds ratio (OR) 0.86, p = 0.012], discrepancy of the slope angle (OR 0.8136, p = 0.000) and the preoperative mechanical femorotibial angle (OR 1.09, p = 0.003) were associated with hyperextension.

CONCLUSION

Mobile-bearing TKA with hyperextension over 5° showed worse functional outcomes at the mid-term follow-up, even though no serious complications were observed. Care should be taken to maintain the posterior condylar offset and to match the resection angles in femur and tibia due to the risk of hyperextension and worse functional outcomes.

LEVEL OF EVIDENCE

IV.

Imageless, robotic-assisted total knee arthroplasty combined with a robotic tensioning system can help predict and achieve accurate postoperative ligament balance

Background

Achieving balanced gaps is a key surgical goal in total knee arthroplasty, yet most methods rely on subjective surgeon feel and experience to assess and achieve knee balance intraoperatively. Our objective was to evaluate the ability to quantitatively plan and achieve a balanced knee throughout the range of motion using robotic-assisted instrumentation in a tibia-first, gap-balancing technique.

Methods

A robotic-assisted, gap-balancing technique was used in 121 consecutive knees. After resection of the proximal tibia, a computer-controlled tensioning device was inserted into the knee joint and the pre-femoral-resection knee gaps were acquired dynamically throughout flexion under controlled load. Predicted gap profiles were used to plan the femoral implant by adjusting the implant alignment and position within certain boundaries to achieve a balanced knee throughout the range of flexion. Femoral cuts were then made according to this plan using a miniature robotic-assisted cutting guide. The tensioning device used to measure the pre-femoral-resection gaps was then reinserted into the joint to quantify the final gap balance under known tension. The final gap profiles were then compared with the predictive gap plans.

Results

The overall root mean square error between the predicted and achieved gaps was 1.3 mm and 1.5 mm for the medial and lateral sides, respectively. Use of robotic assistance resulted in over 90% of knees having mediolateral balance within 2 mm across the flexion range. Gaps at 0° flexion were 2 mm smaller than the gaps at 90°. This difference decreased to less than 1 mm when comparing the tibiofemoral gaps at 10°, 45°, and 90°.

Conclusions

Imageless, robotic-assisted total knee arthroplasty accurately predicts postoperative gaps before femoral resections. This allows surgeons to virtually plan femoral implant alignment and optimize gap balance throughout the range of motion. The accurate prediction of gaps throughout the arc of motion combined with precise, robotically assisted femoral resection produces accurate postoperative ligament balance consistently.

Posterior condylar offset influences the intraoperative soft tissue balance during posterior-stabilized total knee arthroplasty

PURPOSE

This study aimed to clarify the influence of the posterior condylar offset (PCO) on intraoperative soft tissue balance including the joint component gap and varus ligament balance measured by an offset-type tensor during posterior-stabilized (PS) total knee arthroplasty (TKA).

METHODS

In this study, 35 patients with osteoarthritis of the knee underwent PS TKA. Intraoperative soft tissue balance including the joint component gap and varus/valgus ligament balance were assessed at 0°, 10°, 45°, 90°, and 135° of flexion with an offset-type tensor that could be used with the femoral component placement and patellofemoral joint reduction. The correlations between the postoperative PCO and the intraoperative soft tissue balance parameters were assessed using simple regression analysis.

RESULTS

The joint component gap at 0° extension was inversely correlated with the PCO (R = -0.41, p < 0.05). The joint component gap of 10°-0° was positively correlated with the PCO (R = 0.35, p < 0.05). No other soft tissue balance parameters were correlated with the PCO.

CONCLUSIONS

A larger PCO was confirmed to reduce joint component gap in extension but not always in flexion in PS TKA.

What is the Ideal Degree of Extension After Primary Total Knee Arthroplasty?

BACKGROUND

Few studies have examined flexion contracture at the time of primary total knee arthroplasty (TKA) or how flexion contracture changes over time. The purpose of this study was to assess the ideal degree of extension immediately after TKA and to document postoperative changes in extension and clinical outcomes over 5-year follow-up.

METHODS

This retrospective cohort study included 215 cases of primary TKA. Radiographic evaluations were performed on sagittal radiographs with the patient in the supine position and the knee in gravity and in passive extension using a stress device. Clinical outcomes were also measured. Four groups were defined on the basis of the extension angle during radiological evaluation: group 1, -10° to 0°; group 2, >0° to +5°; group 3, >+5° to +10°; group 4, >+10° in gravity.

RESULTS

There were statistically significant differences in passive extension and gravity extension angles in groups 1, 3, and 4 with time-dependent and time*group (passive vs gravity) analyses, but not in group 2. The flexion contracture angles over 10° in gravity were decreased, although over 5° of flexion contracture remained at the final follow-up. Clinical outcomes were worse in groups 1 and 4 at the final follow-up.

CONCLUSION

An extension angle between 0° and 5° in the passive extension position immediately after TKA can be considered ideal up to 5 years of follow-up. Patients with flexion contracture greater than 5° in passive extension and patients with hyperextension should be followed up to assess whether the condition will worsen.

Posterior condylar offset is an independent predictor of functional outcome after revision total knee arthroplasty

Objectives

Preservation of posterior condylar offset (PCO) has been shown to correlate with improved functional results after primary total knee arthroplasty (TKA). Whether this is also the case for revision TKA, remains unknown. The aim of this study was to assess the independent effect of PCO on early functional outcome after revision TKA.

Methods

A total of 107 consecutive aseptic revision TKAs were performed by a single surgeon during an eight-year period. The mean age was 69.4 years (39 to 85) and there were 59 female patients and 48 male patients. The Oxford Knee Score (OKS) and Short-form (SF)-12 score were assessed pre-operatively and one year post-operatively. Patient satisfaction was also assessed at one year. Joint line and PCO were assessed radiographically at one year.

Results

There was a significant improvement in the OKS (10.6 points, 95% confidence interval (CI) 8.8 to 12.3) and the SF-12 physical component score (5.9, 95% CI 4.1 to 7.8). PCO directly correlated with change in OKS (p < 0.001). Linear regression analysis confirmed the independent effect of PCO on the OKS (p < 0.001) and the SF-12 physical score (p = 0.02). The overall rate of satisfaction was 85% and on logistic regression analysis improvement in the OKS (p = 0.002) was a significant predictor of patient satisfaction, which is related to PCO; although this was not independently associated with satisfaction.

Conclusion

Preservation of PCO should be a major consideration when undertaking revision TKA. The option of increasing PCO to balance the flexion gap while maintaining the joint line should be assessed intra-operatively.

Cite this article: N. D. Clement, D. J. MacDonald, D. F. Hamilton, R. Burnett. Posterior condylar offset is an independent predictor of functional outcome after revision total knee arthroplasty. Bone Joint Res 2017;6:172–178. DOI: 10.1302/2046-3758.63.BJR-2015-0021.R1.

Effect of posterior condylar offset on clinical results after posterior-stabilized total knee arthroplasty

PURPOSE

To determine the effect of the posterior condylar offset (PCO) on clinical results after total knee arthroplasty (TKA) using a high-flex posterior-stabilized (PS) fixed-bearing prosthesis.

METHODS

We prospectively studied the clinical and radiographic materials of 89 consecutive female patients (89 knees), who had undergone primary TKAs for end-stage osteoarthritis. All operations were performed by a single senior surgeon or under his supervision using the same operative technique. Based on the corrected PCO change, we divided all cases into two groups: group A (corrected PCO change ≥0 mm, 58 knees) and group B (corrected PCO change<0 mm, 31 knees). One-year postoperatively, clinical and radiographic variables from the two groups were compared by independent t-test. The associations between the corrected PCO changes and the improvements of clinical variables in all patients were analyzed by Pearson linear correlation.

RESULTS

One-year postoperatively, the Knee Society Scores, the Western Ontario and McMaster Universities Osteoarthritis Index, non-weight-bearing active and passive range of knee flexion, flexion contracture, extensor lag, and their improvements had no statistical differences between the two groups (all p>0.05). The corrected PCO change was not significantly correlated with the improvement of any clinical variable (all p>0.05). Group A demonstrated greater flexion than group B during active weight bearing (p<0.05).

CONCLUSIONS

Restoration of PCO plays an important role in the optimization of active knee flexion during weight-bearing conditions after posterior-stabilized TKA, while it has no benefit to non-weight-bearing knee flexion or any other clinical result.

Capsular release around the intercondylar notch increases the extension gap in posterior-stabilized rotating-platform total knee arthroplasty

BACKGROUND

In posterior-stabilized (PS) total knee arthroplasty (TKA), various post-cam designs can be used. A larger cam of the femoral component may tighten the extension gap. Few studies have investigated the relationship between capsular release around the intercondylar notch and the extension gap. The aim of this study was to assess the effect of capsular release around the intercondylar notch on the extension gap.

METHODS

Forty-eight patients (54 knees) who underwent PS rotating-platform TKA (PFC Sigma RP-F) were enrolled retrospectively. We measured the extension gap with and without a femoral trial using a knee balancer, applying a joint distraction force of 44lb. When an intraoperative flexion contracture of >5° persisted, we performed a capsular release approximately 10mm cranial to the intercondylar notch. After full knee extension was achieved, the extension gap was measured again.

RESULTS

Thirty knees required capsular release. With a trial, the medial and lateral differences between the extension gaps before and after capsular release were 1.7mm (p<0.0001) and 2.3mm (p<0.0001), respectively. Without a trial, the gaps were enlarged by 0.4mm (p=0.0452) and 0.6mm (p=0.0215), respectively. Twenty-four knees did not require release. No significant differences were noted in the range of motion at one-year follow-up between the two cohorts.

CONCLUSIONS

With PS rotating-platform TKA, capsular release around the intercondylar notch is found to increase the extension gap and may prevent postoperative flexion contracture.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Ligament balancing in total knee arthroplasty-Medial stabilizing technique

Ligament balancing is one of the most important surgical techniques for successful total knee arthroplasty. It has traditionally been recommended that medial and lateral as well as flexion and extension gaps are equal. This article reviews the relevant literature and discusses the clinical importance of the aforementioned gaps. Current evidence indicates that achieving medial stability throughout the range of motion should be a high priority in ligament balancing in total knee arthroplasty. Finally, the medial stabilising surgical technique, which aims to achieve good medial stability in posterior cruciate-retaining total knee arthroplasty, is introduced.

Influence of Intraoperative Soft Tissue Balance on Postoperative Active Knee Extension in Posterior-Stabilized Total Knee Arthroplasty

We evaluated the influence of intraoperative soft tissue balance on postoperative active knee extension using Offset Repo-Tensor® among 73 varus osteoarthritic knees underwent primary posterior-stabilized total knee arthroplasty. The joint center gap between osteotomized surfaces and the component gap after femoral trial component placement were measured using a joint distraction force of 40lb. The active knee extension angle was measured 4weeks after surgery. The postoperative extension angle was not correlated with the joint center gap at 0°, but positively correlated with the component gap at 0°, and the joint looseness at 0° which was calculated by subtracting insert thickness from the component gap. Thus, intraoperative soft tissue measurement with femoral trial component placement would be useful to predict the postoperative knee extension angle.

Extension gap needs more than 1-mm laxity after implantation to avoid post-operative flexion contracture in total knee arthroplasty

PURPOSE

In total knee arthroplasty (TKA), a high soft-tissue tension in extension at the time of operation would cause a post-operative flexion contracture. However, how tight the extension gap should be during surgery to avoid a post-operative flexion contracture remains unclear. The hypothesis is that some laxity in the intraoperative extension gap is necessary to avoid the post-operative flexion contracture.

METHODS

A posterior-stabilized TKA was performed for 75 osteoarthritic knees with a varus deformity. The intraoperative extension gap was measured using a tensor device that provides the gap length and the angle between the femoral component and the tibial cut surface. The medial component gap was defined as the gap calculated by subtracting the selected thickness of the tibial component, including the polyethylene liner, from the extension gap at the medial side. Then, the patients were divided into three groups according to the medial component gap, and post-operative extension angle measured 1 year after the surgery was compared between each groups.

RESULTS

One year post-operatively, a flexion contracture of more than 5° was found in 0/34 patients when the medial component gap was more than 1 mm, in 2/26 (8%) patients when the gap was between 0 and 1 mm, and in 3/15 (20%) patients when the gap was <0 mm. Three factors were associated significantly with the post-operative extension angle: age, preoperative extension angle, and medial component gap.

CONCLUSION

The intraoperative extension gap is related to the post-operative extension angle. Surgeons should leave more than 1-mm laxity after the implantation to avoid the post-operative flexion contracture. As a clinical relevance, this study clarified the optimal extension gap to avoid the post-operative flexion contracture.

LEVEL OF EVIDENCE

Prospective comparative study, Level II.

Joint gap measurement in total knee arthroplasty using a tensor device with the same articulating surface as the prosthesis

BACKGROUND

We developed a new tensor to measure the joint gap throughout knee flexion during total knee arthroplasty (TKA). This tensor has the same articular shape as that of the tibial liner, including the post structure and the curvature of femorotibial articular surface, to measure the gap intraoperatively under the same conditions as after TKA. The present study aimed to examine the precision of the new tensor for gap measurement after implantation.

METHODS

We performed TKA using the modified gap technique in four cadaveric knees and measured the gaps using the new tensor. The intra-observer and inter-observer error of the tensor was analyzed using 168 measurements of the gaps as determined at least twice by two surgeons. In addition, the gaps in rotating-platform posterior-stabilized TKA were measured at seven positions with the knee bending from extension to full flexion.

RESULTS

The inter-observer and intra-observer errors were 0.8 and 0.3 mm, respectively, indicating precise and reproducible gap measurement. The gaps before implantation in reduced patellar position were 12.1 mm at extension and 12.5 mm at 90° flexion. The gaps after implantation were 9.1, 12.9, 13.1, 13.5, 13.8, 13.3, and 10.1 mm at 0°, 30°, 45°, 60°, 90°, 120°, and full flexion, respectively.

CONCLUSIONS

The new tensor provides precise and reproducible measurements. Although the joint gap before implantation was parallel and equal at extension and 90° flexion, the joint gap after implantation was variable throughout knee flexion. This feature of the gap should be considered during the operation.

Different pattern in gap balancing between the cruciate-retaining and posterior-stabilized total knee arthroplasty

PURPOSE

In order to permit soft tissue balance under more physiological conditions during total knee arthroplasties (TKAs), an offset-type tensor was developed to obtain soft tissue balancing throughout the range of motion with reduced patello-femoral (PF) and aligned tibiofemoral joints. The main purpose of the present study was to assess intra-operative soft tissue balance using a navigation system with the offset-type tensor in both cruciate-retaining (CR) and posterior-stabilized (PS) TKAs.

METHODS

One hundred and twenty TKAs--80 CR and 40 PS--were performed in patients with varus-type osteoarthritis using a computed tomography-free navigation system. The offset-type TKA tensor with a reduced and repaired PF joint and femoral component in place was used with the tibia first gap technique to balance soft tissues (joint component gap and ligament balance) at 0°, 10°, 30°, 60°, 90°, and 120° of flexion. The achievement in equalized rectangular gap at extension and flexion--joint component gap within ±3 mm between extension and flexion and ligament balance within ±3° at extension and flexion--was assessed retrospectively.

RESULTS

Both types of implants showed similar patterns of soft tissue balance throughout the range of motion, whereas PS TKA had larger values especially at 60° or 90° of flexion than did CR TKA. In the achievement of equalized rectangular gaps at extension and flexion, CR TKA was superior to PS TKA.

CONCLUSION

Using the tibia first gap technique with the tensor allows appropriate soft tissue balancing, especially in CR TKA.

LEVEL OF EVIDENCE

Therapeutic studies, Level II.

Posterior femoral condylar offset after total knee replacement in the risk of knee flexion contracture

The aim of this study was to clarify the risk of knee flexion contracture associated with a posterior femoral condylar offset after total knee replacement (TKR). Radiographs from 100 healthy Japanese volunteers were included in the study. We evaluated femoral component posterior offset in various implants and compared them with the normal Japanese knee. Posterior offset of the femoral condyle is up to a maximum of 4.7 times greater than that of the healthy Japanese knee in all knee implants. Excess posterior offset of the femoral condyle in TKR prostheses may cause knee joint flexion contracture due to the relative shortening of the posterior soft tissue.

Lateral soft tissue laxity increases but medial laxity does not contract with varus deformity in total knee arthroplasty

BACKGROUND

In TKA, soft tissue balance (the joint gap) depends on the amount of resected bone and soft tissue release. Some studies report preoperative bony deformity correlates with soft tissue balance evaluated intraoperatively and that the medial tissues are contracted with varus deformity. However, these studies did not take into account the amount of resected bone and did not describe whether the soft tissue was tight or loose. Therefore, it remains unclear whether in varus deformity the soft tissues on the medial side are contracted.

QUESTIONS/PURPOSES

We compared (1) intraoperative joint gap, (2) amount of resected bone, and (3) intraoperative soft tissue laxity on the lateral and medial sides according to severity of preoperative varus deformity.

METHODS

We retrospectively reviewed 70 patients with osteoarthritis and varus deformities who underwent 90 TKAs. We retrospectively divided the 90 knees into three groups according to degree of preoperative alignment: mild varus group (<10°), moderate varus group (10°-20°), and severe varus group (>20°). To evaluate intraoperative soft tissue tension, we calculated the soft tissue gap by subtracting the thickness of the resected bone from the joint gaps on the medial and lateral sides, respectively. We then explored the relationship between the soft tissue gap and preoperative alignment.

RESULTS

The lateral soft tissue gap was larger in the severe varus group than in the mild and moderate varus groups. The medial soft tissue gap was larger in the severe varus group than in the mild varus group, but there were no differences in the medial joint gaps among the groups.

CONCLUSIONS

After the bone is resected, the soft tissue on the lateral side is more lax; however, the soft tissue on the medial side is not shorter with greater preoperative varus deformity.