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

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.

A tensor with a flat surface overestimates midflexion laxity in total knee arthroplasty: Comparison between a tensor with a flat-shaped surface and a tensor with an insert-shaped surface

BACKGROUND

Soft tissue balance is important for the success of total knee arthroplasty (TKA). Various types of tensors have been developed for the precise measurement of a gap. We hypothesized that the surface shape of the tensor that contacted the TKA component affected the gap measurement. This study aimed to compare the gaps obtained with flat and insert-shaped surface tensors.

METHODS

Two senior surgeons performed 95 TKAs (Vanguard-PS:55 knees; Persona-PS:40 knees). The joint gap was measured in each static knee flexion status (0°, 30°, 45°, 60°, 90°, 120°, and full flexion). We compared the gaps measured with a flat surface tensor and an insert-shape surface tensor. We defined a significant change as a gap difference of >1 mm with a statistical significance.

RESULTS

In Vanguard-PS, significant changes were observed at 30° and 45°. In Persona-PS, significant changes were observed at 30°, 45°, and 60°. In both implants, gaps measured with the flat tensor were larger than those measured with the insert tensor at approximately midflexion, and the significant changes disappeared in higher flexion position over midflexion.

CONCLUSIONS

The surface shape of the tensor affected the measurement of midflexion laxity in TKA. When measuring the gap with a flat tensor, the midflexion laxity was overestimated. A tensor with an insert-shaped surface should be used to measure the gap in TKA.

Preoperative and intraoperative factors contributing to patient satisfaction after bi-cruciate stabilized total knee arthroplasty

BACKGROUND

One of the causes of dissatisfaction following total knee arthroplasty (TKA) is abnormal knee kinematics. A newly designed bi-cruciate stabilized (BCS) TKA system has been developed to produce close-to-normal kinematics because of its anatomic tibiofemoral articular geometry and cam-post mechanism. Although BCS TKA is expected to improve patient satisfaction, no reports have described the appropriate technique or soft tissue handling required to achieve excellent satisfaction with BCS TKA. This study is to identify preoperative and intraoperative predictors of patient satisfaction after BCS TKA.

METHODS

Altogether, we studied 113 knees with primary varus knee osteoarthritis that underwent BCS TKA with a navigation system. Preoperative parameters including Knee Society Score and patient-reported scores [the Knee injury and Osteoarthritis Outcome Score (KOOS)] and intraoperative parameters including coronal, sagittal and axial alignment and joint laxity in each compartment that affected patient satisfaction was evaluated. Satisfaction score was evaluated with use of the 2011 Knee Society Scoring system. The multivariate regression analysis included age and preoperative and intraoperative parameters that correlated with satisfaction scores in the univariate analysis (P < 0.05).

RESULTS

The mean satisfaction score was 28.2 ± 6.1. Multivariate regression analysis showed that the predictors of patient satisfaction were a preoperative high KOOS score for activities of daily living (P < 0.001), male sex (P = 0.005), older age (P = 0.027), and minimal medial joint laxity during flexion (P = 0.031).

CONCLUSION

When performing BCS TKA, surgeons should pay attention to maintaining proper stability of the medial compartment, especially during flexion.

Optimal Distraction Force for Evaluating Tibiofemoral Joint Gaps in Posterior Stabilized Total Knee Arthroplasty

BACKGROUND

Obtaining well-balanced soft tissues is important to achieve natural knee kinematics after total knee arthroplasty (TKA). In conventional procedures, soft tissue balance is evaluated with spacer blocks or lamina spreaders. However, the evaluation depends on the surgeons' experience and is not quantitative. This study aims to measure the mechanical properties of knee soft tissue with a new ligament balancer and to determine the optimal distraction force for evaluating tibiofemoral joint gaps in TKA.

METHODS

This study included 30 consecutive patients with medial knee osteoarthritis who were scheduled to undergo posterior stabilized TKA. The mean age of patients was 73 ± 9.6 years at the time of surgery, and the mean hip-knee-ankle angle was 13.1 ± 6.5° in varus. After distal femoral and proximal tibial resections, the tibiofemoral joint gaps under several distraction forces were measured in extension and at 90° flexion. The load-displacement curves in extension and flexion were drawn with these data, and the stability range, which was defined as the shift range from the toe region to the linear region in the curves, was calculated.

RESULTS

The stability ranges were 160 Newtons (N) in extension and 140 N in flexion.

CONCLUSIONS

These displacement forces were considered optimal for evaluating tibiofemoral joint gaps during surgery and ensuring knee stability after TKA.

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.

Joint distraction force changes the three-dimensional articulation of the femur and tibia in total knee arthroplasty: a cadaveric study

PURPOSE

The purpose of this study was to test the hypotheses that the joint distraction force changes the three-dimensional articulation between the femur and the tibia and that the presence of posterior cruciate ligament (PCL) affects the three-dimensional articulation during joint gap evaluation in total knee arthroplasty (TKA).

METHODS

Cruciate-retaining TKA procedures were performed on 6 cadaveric knees using a navigation system. The joint center gap and varus ligament balance were measured using Offset Repo-Tensor^® with the knee at 90° of flexion before and after PCL resection for joint distraction forces of 89, 178, and 266 N. The three-dimensional location of the tibia relative to the femur and the axial rotational angle of the tibia were also assessed.

RESULTS

Regardless of PCL resection, the joint center gap became larger (p = 0.002, p = 0.020) and varus ligament balance became more varus (p = 0.002, p = 0.002) with increasing joint distraction force, whereas the tibia was more internally rotated (p = 0.015, p = 0.009) and more anteriorly located (p = 0.004, p = 0.009). The tibia was more internally rotated (p = 0.015) and more posteriorly located (p = 0.026) after PCL resection than before resection.

CONCLUSIONS

Joint distraction force changed three-dimensional articulation regardless of PCL preservation. PCL function was revealed as a factor restraining both tibial posterior translation and internal rotation. Surgeons should recognize that joint gap evaluation using a tensor device is subject to three-dimensional changes depending on the magnitude of the joint distraction force.

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.

Changes in postoperative extension angle after total knee arthroplasty: Effect of polyethylene insert thickness

BACKGROUND

Flexion contracture is a serious complication after total knee arthroplasty (TKA). Polyethylene insert (PE) thicker than the extension gap during surgery causes flexion contracture. The purpose of this study was to identify the changes over time in postoperative extension angle and the correlation between extension gap and PE thickness.

METHODS

Overall, 127 knees were analyzed to evaluate the changes in extension angle over time. "Gap difference" was defined as the distance obtained by subtracting the extension gap from the PE thickness. Patients were divided into four groups according to gap difference (0-3 or greater mm). We evaluated the correlation of gap difference and changes in postoperative extension angle over time.

RESULTS

The extension angles of all knees were -4.2 ± 3.9 (deg. mean ± s.d.) at surgery, -5.9 ± 5.7 at 3 months, -3.4 ± 5.4 at 6 months, and -1.3 ± 5.4 at 2 years. Gap difference was negatively correlated with the extension angle at surgery and at 2 years (r = 0.40, r = 0.36). The extension angles at 2 years in each group (groups 0, 1, 2, 3 or greater) were 2.0°±4.7°, -0.8°±5.3°, -3.4°±5.3°, -4.0°±4.1° (p < 0.05), respectively.

CONCLUSIONS

The extension angle became worse at 3 months compared to that at surgery (p = 0.01) and then improved until 2 years. The correlation between gap difference and extension angle was maintained at 2 years, and thicker PE caused flexion contracture even after 2 years. Hence, PE selection considering the extension gap is important.

Joint Gap in Mid-Flexion Is Not a Predictor of Postoperative Flexion Angle After Total Knee Arthroplasty

BACKGROUND

Postoperative knee flexion angle is one of the most important outcomes of total knee arthroplasty (TKA). Intraoperative ligament balancing may affect the postoperative range of motion of the knee. However, the relationship between intraoperative ligament balancing and postoperative flexion angle was still controversial. The purpose of this study was to determine whether intraoperative joint gap affects postoperative knee flexion angle or not.

METHODS

Prospective multicenter study of 246 knees with varus osteoarthritis undergoing a posterior-stabilized, mobile-bearing TKA was performed. The joint gap before implantation and after implantation was measured. The joint gap after implantation was measured using a specially designed tensor device with the same shape of a total knee prosthesis at 0°, 30°, 60°, 90°, 120°, and 145° of flexion with the reduction of the patellofemoral joint. Stepwise multiple regression analysis was conducted to determine the predictors of the flexion angle of the knee after the operation.

RESULTS

Predictors were identified in the following 3 categories: (1) preoperative flexion angle, (2) intraoperative flexion angle, and (3) joint gap looseness at 120° of flexion (joint gap after implantation at 120° of flexion - joint gap after implantation at 0° of flexion) (R = 0.472, P < .01).

CONCLUSION

Flexion angle after TKA was not affected by the flexion joint gap looseness before implantation and the joint gap looseness after implantation from 30° to 90° of flexion. Surgeons should notice that joint gap looseness in mid-flexion range did not increase the postoperative knee flexion angle.

Is the Use of Spreaders an Accurate Method for Ligament Balancing?

BACKGROUND

To analyze 2 methods of manual spreader gap assessment accuracy, visual vs blinded, compared with a controlled tensioner in total knee arthroplasty.

METHODS

Twenty-two fresh frozen cadaver knees were used to perform total knee arthroplasty by 22 surgeons. Extension and flexion gaps were measured with empirical manual force application with spreaders in 2 different manners: (1) surgeons were blinded to gap geometry formation-blind method group (BM) and (2) surgeons viewed them-viewing method group (VM). A tensioner was used to measure the corresponding ligament tension applied during spreader measurements and to measure the extension and flexion gaps with standard force of 100 and 80 N (tensioner method [TM]) in each femorotibial compartment.

RESULTS

All measurements with spreaders (VM and BM) presented extension and flexion gaps oversized and asymmetric (P < .0001), when compared with the same gaps measured with the tensioner. Approximately 63% (P = <0.001) and 77.3% (P = .161) of the VM group and 68.2% (P = .018) and 77.3% (P = .161) of the BM group demonstrated asymmetry for extension and flexion gaps up to 3 mm to the TM. Gaps measured in the VM group presented results with slightly less oversizing and asymmetries than the measurements in the BM group compared with TM, although significantly different (P < .0001).

CONCLUSION

The assessment of extension and flexion gaps with empirical manual applied force spreaders produced oversized and asymmetric gaps compared with the use of tensioner. No visual influence was observed during the spreader applied empirical manual force compared with the blinded assessment.

Outcome in total knee arthroplasty with a medial-lateral balanced versus unbalanced gap

PURPOSE

To evaluate the clinical outcome in 108 total knee arthroplasty (TKA) patients with a medial-lateral balanced versus unbalanced gap after a mean follow-up of 34 months.

METHODS

64 women and 44 men (mean age, 69.5 years) underwent computer-assisted TKA for osteoarthritis using a cemented fixed-bearing cruciate-retaining prosthesis. The medial-lateral gap difference (measured with the prosthesis in situ and the patella reduced) was balanced (≤2 mm) in 81 patients and unbalanced (>2 mm) in 27 patients. After a mean follow-up of 34 months, patients were assessed using the Western Ontario and McMaster Universities Arthritis Index (WOMAC) questionnaire for pain, stiffness, and physical function. Scores were normalised to 0% (worst) to 100% (best).

RESULTS

The balanced and unbalanced gap groups were comparable in terms of age, severity of osteoarthritis, and proportion of pre- and post-operative mechanical alignment. Compared with the balanced gap group, the unbalanced gap group had a larger medial-lateral extension gap difference (0.75±0.57 vs. 2.02±1.15 mm, p=0.001) and medial-lateral flexion gap difference (0.79±0.63 vs. 2.98±2.13 mm, p=0.001) and lower normalised total WOMAC score (84.9±18 vs. 74.8±20.8, p=0.017).

CONCLUSION

WOMAC score is better in TKAs with a medial-lateral balanced (<2 mm) gap.

Intraoperative Manipulation for Flexion Contracture During Total Knee Arthroplasty

Joint gap balancing during total knee arthroplasty (TKA) is important for ensuring postoperative joint stability and range of motion. Although the joint gap should be balanced to ensure joint stability, it is not easy to achieve perfect balancing during TKA. In particular, relative extension gap shortening can induce flexion contracture. Intraoperative manipulation is often empirically performed. This study evaluated the tension required for this manipulation and investigated the influence of intraoperative manipulation on the joint gap in cadaveric knees. Total knee arthroplasty was performed in 6 cadaveric knees from whole body cadavers. Flexion contracture was induced using an insert that was 4 mm thicker than the extension gap, and intraoperative manipulation was performed. Study measurements included the changes in the joint gap after manipulation at 6 positions, with the knee bending from extension to 120° flexion, and the manipulation tension that was required to create a 4-mm increase in the gap. The manipulation tension needed to create a 4-mm increase in the extension gap was 303±17 N. The changes in the joint gap after manipulation were 0.4 mm, 0.6 mm, 0.2 mm, -0.2 mm, -0.4 mm, and -0.6 mm at 0°, 30°, 45°, 60°, 90°, and 120° flexion, respectively. Therefore, the joint gap was not significantly changed by the manipulation. Intraoperative manipulation does not resolve flexion contracture. Therefore, if flexion contracture occurs during TKA, treatment with additional bone cutting and soft tissue release is likely more appropriate than manipulation. [Orthopedics. 2016; 39(6):e1070-e1074.].

Decreased extension gap and valgus alignment after implantation of total knee prosthesis in primary varus knees

PURPOSE

It was hypothesised that implantation of a total knee prosthesis may change the size and shape of the joint gap. To test this hypothesis, a tensor device was used which was specifically designed to reproduce the conditions before and after implantation, including attachment of the polyethylene insert trial. This study aimed to compare the joint gaps before and after implantation of a total knee prosthesis using this new tensor device.

METHODS

A total of 259 primary varus knees were included in this study. Knees were exposed using a medial parapatellar approach, and the anterior and posterior cruciate ligaments were resected. After the trial reduction, the intraoperative joint gap kinematics was measured using the tensor device.

RESULTS

Implantation of a total knee prosthesis decreased the size of the extension joint gap and made it valgus, but did not influence the size or shape of the flexion joint gap.

CONCLUSIONS

The present findings suggest that the classical gap technique, which creates equal and rectangular extension and flexion joint gaps in the bone cutting surface, results in an imbalance between the extension and flexion joint gaps after implantation. To achieve equal and rectangular extension and flexion joint gaps after implantation, the prepared extension joint gap should be about 2 mm larger than the flexion joint gap and slightly varus before implantation in primary varus knees.

LEVEL OF EVIDENCE

Therapeutic study, Level II.

Midflexion Laxity After Implantation Was Influenced by the Joint Gap Balance Before Implantation in TKA

The relationship between the joint gap before and after implantation in 259 knees during the total knee arthroplasty was investigated using a tensor device which can attach the polyethylene insert trial. Patients were divided into following 3 groups according to the joint gap balance before implantation (flexion joint gap--extension joint gap); group 1: >1mm; group 2: -1 to 1mm, and group 3: <-1mm. Joint gap after implantation was loose at 30°, 60°, 90°, and 120° of flexion in group 1 and 2, but loose only at 30° of flexion in group 3 (p<0.01). This study showed that loose flexion joint gap before implantation increased the risk of joint gap laxity after implantation especially at midflexion ranges.