Navigation-assisted total knee arthroplasty in knees with osteoarthritis due to extra-articular deformity

3D-printed, patient-specific cutting guides improve femoral and tibial cut alignment in canine total knee replacement

OBJECTIVES

The purpose of this cadaveric study was to determine whether patient-specific guides (PSGs) improve the accuracy of tibial and femoral cut alignment in canine total knee replacement (TKR), as compared with generic cutting guides.

STUDY DESIGN

Original research.

ANIMALS

Sixteen pelvic limbs from skeletally mature medium- to large-breed canine cadavers.

METHODS

Specimens were randomly allocated to one of two groups (PSG or Generic; N = 8/group). In the Generic group, femoral and tibial ostectomies were made using the standard canine TKR femoral cutting blocks and tibial alignment guide. In the PSG group, the cuts were made using a series of custom 3D-printed cutting guides. "Planned" and "actual" tibial and femoral cut alignments were compared in the frontal and sagittal planes, and errors were calculated by subtracting actual from planned values.

RESULTS

Use of 3D-printed PSGs improved tibial cut alignment in the frontal plane but not the sagittal plane. PSGs also improved the alignment of the cranial and distal femoral ostectomies but did not impact varus-valgus alignment.

CONCLUSIONS

These findings support the use of PSGs for TKR in dogs. Clinical trials are now needed to determine whether the benefits of PSGs translate into measurable improvements in joint function and implant longevity.

CLINICAL SIGNIFICANCE

PSGs have the potential to improve femoral and tibial component alignment in canine TKR.

Robotic-assisted TKA reduces surgery duration, length of stay and 90-day complication rate of complex TKA to the level of noncomplex TKA

INTRODUCTION

Complex primary total knee arthroplasties (TKA) are reported to be associated with excessive episode of care (EOC) costs as compared to noncomplex procedures. The impact of robotic assistance (rTKA) on economic outcome parameters in greater case complexity has not been described yet. The purpose of this study was to investigate economic outcome parameters in the 90-days postoperative EOC in robotic-assisted complex versus noncomplex procedures.

MATERIALS AND METHODS

This study is a retrospective, single-center review of 341 primary rTKAs performed between 2017 and 2020. Patient collective was stratified into complex (n = 218) and noncomplex TKA (n = 123) based on the presence of the following criteria: Obese BMI, coronal malalignment, flexion contracture > 10°, posttraumatic status, previous correction osteotomy, presence of hardware requiring removal during surgery, severe rheumatoid arthritis. Group comparison included surgery duration, length of stay (LOS), surgical site complications, readmissions, and revision procedures in the 90-days EOC following rTKA.

RESULTS

The mean surgery duration was marginally longer in complex rTKA, but showed no significant difference (75.26 vs. 72.24 min, p = 0.258), neither did the mean LOS, which was 8 days in both groups (p = 0.605). No differences between complex and noncomplex procedures were observed regarding 90-days complication rates (7.34 vs. 4.07%, p = 0.227), readmission rates (3.67 vs. 3.25%, p = 0.841), and revision rates (2.29 vs. 0.81%, p = 0.318).

CONCLUSIONS

Robotic-assisted primary TKA reduces the surgical time, inpatient length of stay as well as 90-days complication and readmission rates of complex TKA to the level of noncomplex TKA. Greater case complexity does not seem to have a negative impact on economic outcome parameters when surgery is performed with robotic assistance.

Custom-made hinged total knee arthroplasties in the context of extra-articular deformity: a case series

PURPOSE

Treatment of secondary knee osteoarthritis with a significant extra-articular deformity can be challenging. In such cases, an osteotomy or a custom-made hinged knee arthroplasy (CMH) are treatment options. However, there are limited data on the outcomes of using CMHs. Thus, the aim of this retrospective study was to assess the clinical results and subjective outcomes of CMHs.

METHODS

We reviewed 9 CMHs (Endo-Model, LINK) in 7 patients with a minimum of 2-year follow-up. Upon the last follow-up, we evaluated MA, stability and range of movement (ROM). Oxford Knee Score (OKS) was used to evaluate patient-reported outcomes.

RESULTS

The average age upon surgery was 61 years (48-76 years), and the follow-up period was 66 months. There were no early complications. Two CMHs were revised, one due to aseptic loosening and one due to late-onset haematogenic infection. Pre-operatively, MA varied from 18° (average 11°) valgus-deformity to 30° (average 17°) varus-deformity. Post-operatively, 7/9 (78%) of patients achieved better MA. Upon follow-up, the average OKS was 41/48, and ROM was 113°.

CONCLUSIONS

Patients treated with CMHs achieved good clinical and patient-reported outcomes. There were no early reoperations, and revision rate was relatively low. Overall, CMH could be considered for low-demand patients with increased operative risks.

Knee osteoarthrosis with extra-articular femoral deformity treated with total knee arthroplasty: A case series

A successful Total knee arthroplasty (TKA) procedure requires restoration of mechanical axis and soft tissue balancing. Deformity of tibia and femur occurs with history of trauma or osteotomy, infection, metabolic bone disease and excessive bowing. Tackling pre-existing extra-articular deformity of lower limbs during total knee arthroplasty can be challenging due to difficulty in restoring alignment axis and soft tissue balancing. We have recorded 6 patients underwent total knee arthroplasty with preexisting extra-articular femoral deformity by intra-articular correction from 1995 to 2017. All patients had extra-articular deformity of the femur due to fracture malunion which were treated either conservatively, plating or intra-medullary nail. Coronal deformity is corrected from an average of 15.5 degrees to 4.6 degrees from neutral axis. Sagittal deformity is corrected from average of 6.8 degrees to 3.6 degrees. One patient developed progressive genu recurvatum at 7 years follow-up with range of motion at 25 degrees extension and 110 degrees flexion. The average pre-operative Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score was 68.5 (range 51−87) decreased to 50.7 (range 21–71) at 12 months post-operative and Knee score averaged 53.3 (range 51–55) increased to an average of 88.5 (range 82–94). There was only one revision for aseptic loosening 16 years after total knee replacement (TKR) and no other cases of radiological sign of aseptic loosening. In conclusion, Intra-articular correction of an extra articular femoral deformity for TKR is an attractive approach in mild to moderate deformity further from the knee joint.

Extra-articular tibial deformity management in total knee replacement

BACKGROUND

Presence of an extra-articular deformity in the femur or tibia poses a challenge to the surgeon undertaking knee replacement procedure. The conundrum is whether to correct the deformity beforehand, or accept the deformity and compensate for this through placement of the implant.

MATERIAL AND METHODS

This is a retro-spective study comprising six patients who had a knee replacement in the presence of an extra-articular deformity of the tibia treated at our centre. All six had the knee replacement without correction of deformity. The data evaluated included clinical outcome, mechanical axis correction, type of implant, and the use of any software / computer guidance.

The deformity was managed through planning of tibial resection without the need for pre-operative deformity correction.

RESULTS

Mean age was 66.5 years. Mean coronal plane deformity in the tibia was 8.6 degrees. The hip- knee-ankle improved from a mean 12.6 degrees to 4 degrees. Mean Oxford knee score improved from a mean of 19 to 33.6.

CONCLUSION

Planning the tibial resection on the basis of mechanical axis of tibia allows correction of alignment without the need for preoperative correction.

Correction of the deformity may not be needed if the maximum tibial resection is less than 15 mm.

Handheld computer-navigated constrained total knee arthroplasty for complex extra-articular deformities

INTRODUCTION

The present study aimed to assess the postoperative alignment and clinical outcomes of patients with complex extra-articular deformities (EADs) undergoing computer-assisted surgery (CAS) for constrained total knee arthroplasty (TKA) with modular stem extensions.

MATERIALS AND METHODS

From May 2015 to July 2018, ten patients with EADs scheduled for constrained TKA were enrolled retrospectively. The preoperative average deviation from neutral (= 180°) mechanical axis was 15.3° (range of coronal alignment: 150.9° varus-202.9° valgus). Alignment was assessed using an accelerometer-based handheld CAS system. On long-leg films, the positions of the components and possible stems were analysed and templated preoperatively. The average follow-up was 3.3 years (range: 2.0-4.6 years).

RESULTS

The postoperative mechanical axis was within ± 3.0° from neutral in nine patients. In all patients, the Knee Society score (KSS) and range of motion improved significantly. A constrained condylar and a rotating hinge prosthesis were used in five patients each. In eight patients, the 100-mm cementless stem that was preferred by the authors was found to be unusable for the femur or the tibia in the planning stage. For the femur, a cementless 100-mm stem was used in three, and a cemented 30-mm stem in five patients; a femoral stem was not usable in two patients. For the tibia, a cementless 100-mm stem was used in six, and a cemented 30-mm stem in two patients; a monoblock rotating hinge tibia was used in two patients.

CONCLUSIONS

Complex EADs were excellently managed during constrained TKA implantation using the handheld CAS system. Templating allowed the possible stem lengths to be identified and prevented anatomical conflict with the CAS-configured mechanical alignment. Limb alignment and function improved significantly after surgery. No intra- or postoperative complications occurred.

LEVEL OF EVIDENCE

Level IV, retrospective study.

Outcomes of complex primary total knee arthroplasties performed with custom cutting guides

BACKGROUND

Total knee arthroplasty (TKA) is particularly challenging in patients with marked deformities or existing hardware due to the inability to use traditional instrumentation. One potential technique to mitigate this obstacle is the use of patient-specific cutting guides. The purpose of this study was to evaluate the use of custom cutting guides in complex primary TKAs.

METHODS

Twenty complex TKAs performed in 18 patients were identified. Of these, 11 were performed in patients with existing hardware, three in patients with dwarfism, three in patients with post-traumatic deformities, two in a patient with multiple epiphyseal dysplasia, and one in a patient with a large deformity from Blount's disease. All prior hardware was retained. One patient died from unrelated causes three months following surgery. The remaining patients were followed for a mean of 5.2 years (range: 1.2-9.7 years).

RESULTS

One patient sustained a non-displaced, medial tibial plateau fracture intra-operatively that was successfully treated with plating. Mean operative time was 112.1 ± 44.4 min, and mean hospital stay was 2.7 ± 1.6 days. Average deviation from the mechanical axis improved from 10.5° pre-operatively to 3.1° postoperatively (P < 0.001). Average Knee Society Scores improved from 48.1 to 77.4 points (P < 0.001). Mean extension improved from 5.9° to 1.4° (P = 0.049). Two patients subsequently required a manipulation under anesthesia, and one patient had delayed wound healing that resolved without surgery.

CONCLUSIONS

Custom cutting guides are a viable option in complex primary TKAs where the use of traditional instrumentation would be challenging.

Custom TKA enables adequate realignment with minimal ligament release and grants satisfactory outcomes in knees that had prior osteotomies or extra-articular fracture sequelae

PURPOSE

To report the early clinical and radiographic outcomes of custom total knee arthroplasty (TKA) in knees that had prior osteotomies and/or extra-articular fracture sequelae.

METHODS

The authors retrospectively analysed a consecutive series of 444 knees that received custom TKA between 2016 and 2019 and identified 41 knees that had prior extra-articular events (osteotomies or fracture sequelae). Patients responded to pre- and post-operative (> 12 months) questionnaires, including Knee Society Score (KSS), Oxford Knee Score (OKS), Forgotten Joint Score (FJS) and Knee injury and Osteoarthritis Outcome Score (KOOS). Net improvements were calculated by subtracting pre- from post-operative scores. In addition to a preoperative CT scan, pre- and post-operative long-leg weight-bearing radiographs were obtained, on which the hip-knee-ankle (HKA) angle, femoral mechanical angle (FMA, between femoral mechanical axis and joint line) and tibial mechanical angle (TMA, between tibial mechanical axis and joint line) angles were measured, and alignment was planned within a 'target zone' of FMA and TMA within 85°-95° and HKA angle within 175°-183°. Agreements between preoperative, planned and post-operative angles were calculated using intra-class correlation coefficients (ICC).

RESULTS

From the initial 41 knees, 3 had incomplete post-operative data and 1 was revised for painful stiffness due to uncorrected rotational malunion, leaving 37 knees for analysis. Twenty had prior osteotomies (tibia, n = 18, femur, n = 2), 8 had isolated fractures (tibial, n = 3; femoral, n = 5), and 9 had both osteotomies and fractures. Postoperative coronal alignments were 90.4° ± 2.4° for FMA, 89.3° ± 2.6° for TMA and 179.9° ± 3.0° for HKA angle. Agreements between planned and achieved alignments were fair to excellent, and 29 (78%) knees were within the 'target zone'. At a mean follow-up of 15 ± 5 months, all clinical scores had improved significantly (p < 0.001).

CONCLUSIONS

Custom TKA granted satisfactory clinical outcomes and a low complication rate in knees that had prior osteotomies and/or extra-articular fracture sequelae. Using custom implants and strategies for coronal alignment, 29 (78%) of the 37 knees were successfully aligned within the 'target zone', and 35 (95%) of the 41 knees did not require ligament release.

LEVEL OF EVIDENCE

IV.

Total Knee Arthroplasty in Patients with Prior Femoral and Tibial Fractures: Outcomes and Risk Factors for Surgical Site Complications and Reoperations

Objective

To investigate the outcomes of total knee arthroplasty (TKA) in patients with a prior femoral or tibial fracture, and identify the risk factors for surgical site complications and reoperations.

Methods

Seventy‐one TKAs performed in 71 patients with a prior tibial or femoral fracture between January 2005 and December 2016 were reviewed retrospectively. Forty males (40 knees) and 31 females (31 knees) were included. The mean age at the time of TKA was 59.2 (range, 29–83) years. Outcomes were assessed using the Knee Society score before surgery and at the final follow‐up visit. The patients' satisfaction rates were evaluated. Complications and reoperations were recorded by clinical and radiographic assessment. Logistic regression analysis was used to identify the risk factors for surgical site complications and reoperations.

Results

The median follow‐up period was 4.7 (range, 3.2–7.1) years. The median knee range of motion increased from 90° preoperatively to 110° at the latest follow‐up. The Knee Society knee score and function score improved from 35 (30, 40) and 40 (30, 50) to 90 (82, 93) and 90 (65, 100), respectively. The degree of overall satisfaction after TKA surgery was very satisfied in 41 patients, satisfied in 20 patients, neutral in four patients, dissatisfied in four patients, and very dissatisfied in two patients. The overall satisfaction (very satisfied and satisfied) rate was 85.9% (61 knees). Twelve knees (16.9%) had 19 surgical site complications. Six knees (8.3%) underwent reoperations, including one revision due to periprosthetic joint infection, one debridement and implant retention for superficial infection, two debridements for delayed wound healing, one open reduction and internal fixation for supracondylar fracture, and one re‐fixation and bone grafting for hardware failure after a combined femoral shaft osteotomy and TKA. Preoperative patella baja was diagnosed in 12 knees, and was identified as a risk factor for surgical site complications and reoperations.

Conclusions

TKA for post‐fracture osteoarthritis significantly relieved pain and improved function, but the incidence of surgical site complications and reoperations was high. Preoperative patella baja was a risk factor for surgical site complications and reoperations.

Management of Extra-articular Deformity in the Setting of Total Knee Arthroplasty

Extra-articular deformities of the femur and tibia in conjunction with advanced knee osteoarthritis pose unique challenges for the arthroplasty surgeon. Careful preoperative planning is needed to evaluate both the intra- and extra-articular deformities and to determine the best route to total knee arthroplasty. An intra-articular compensatory correction can typically be performed if the extra-articular deformity is distant from the joint or if preoperative templating shows that bony cuts do not interfere with ligamentous attachments. Staged osteotomy followed by arthroplasty is beneficial in severe cases in which bony cuts are excessive or would interfere with soft-tissue structures and in cases with leg-length discrepancy. Osteotomies can be performed percutaneously and fixed with intramedullary nails, external fixators, or plate and screw constructs. Ligamentous laxity after correction and risk of peroneal nerve injury are increased in extra-articular deformity cases and must be considered during the knee arthroplasty procedure with increased implant constraint and patient counseling, respectively. Computer-assisted navigation has an emerging role in total knee arthroplasty in patients with extra-articular deformity.

Total Knee Arthroplasty in Patients With Extra-Articular Deformity: Restoration of Mechanical Alignment Using Accelerometer-Based Navigation System

BACKGROUND

Total knee arthroplasty (TKA) in patients with post-traumatic extra-articular deformity (EAD) is difficult to manage using conventional instrumentation techniques. In this study, we evaluate whether accelerometer navigation system can be a valuable option to make accurate bone resections and restore the neutral mechanical axis in complex TKA patients with EAD.

METHODS

From May 2015 to June 2017, 18 consecutive TKA were performed in 18 patients with knee osteoarthritis with associated EAD. An accelerometer-based navigation system was used to guide tibial and femoral resection in the coronal and sagittal plane. Postoperative lower limb alignment in coronal plane and component position in coronal and sagittal plane was measured through full-leg weight-bearing X-ray. Clinical score were recorded using the Knee Society Score at the final follow-up.

RESULTS

The mean hip-knee-ankle angle was 0.9° ± 1.4° varus alignment. The coronal alignment of the femoral component was 89.2° ± 1.9°, and the coronal alignment of the tibial component was 89.4° ± 2.1°. The sagittal alignment of the femoral component was 93.2°± 1.9°, and the sagittal alignment of the tibial component was 84.4° ± 3.1°. At the final follow-up, the Knee Society Score was 89 points (range, 82-100), and the functional score was 86.7 points (range, 60-100). No intraoperative and postoperative surgical complications were reported using this technology.

CONCLUSION

Accelerometer-based navigation is accurate in achieving neutral mechanical alignment and optimal implant position after TKA in patients with EAD. This system should be considered a valuable option to the more complex technique of computer navigation or robotic surgery.

Extra-articular deformities in arthritic knees-a grueling challenge for arthroplasty surgeons: An evidence-based update

Critical to the success of a total knee arthroplasty (TKA) is the anatomical alignment. This may appear as a challenge in an extra-articular deformity (EAD) that may be inherent in certain people or result from fracture malunion, congenital disorders, nutritional, metabolic and infective causes. This appraisal aimed at providing the reader with an up-todate overview of the research carried out on, and existent evidence of EAD correction while planning a TKA. We reviewed the current English literature on TKA in extra-articular knee deformities. Among the published data, a common initial approach of mandatory clinical and radiological assessment emerges as an obligatory step while handling cases with EAD. While several methods of managing the deformity and arthritis have been described, a broad division into intra-articular and extra-articular means can be deciphered. The relatively old-school, yet reliable thought process of extra-articular correction allows an all-inclusive restoration of alignment with the inherent complications related to the necessary osteotomy. A cohort of younger and more venturesome surgeons seem inclined towards performing navigated, intra-articular correction for mild to moderate and sometimes, severe deformities. The crux of the matter lies is obtaining a well-balanced knee without violating the all-important cruciates. Restoring the patient’s ambulatory status seems sooner with the intra-articular methods which are also more precise in determining the axes and while removing minimum bone. Greatest satisfaction is accomplished in those with less grotesque, rotationallyaligned knees while meticulously balancing soft-tissues and encouraging earlier weightbearing.

One-stage computer-assisted total knee arthroplasty and tibial osteotomy

Same-stage tibial osteotomy may deserve consideration in candidates to total knee arthroplasty (TKA) who have severe bone deformities, particularly at extra-articular sites. This strategy obviates the need for either a major and technically difficult ligament release procedure, which may compromise ligament balancing, or the use of a semi-constrained prosthesis. This technical note describes a one-stage, computer-assisted technique consisting in TKA, followed by corrective tibial osteotomy to obtain an overall mechanical axis close to 180° without extensive ligament balancing. This technique provided satisfactory outcomes in 8 patients followed-up for at least 3years, with no specific complications or ligament instability and with a hip-knee-ankle angle close to 180°. After planning, intra-operative computer assistance ensures accurate determination of both implant position and the degree of correction achieved by the osteotomy.

A Comparison of the Medium-Term Results of Total Knee Arthroplasty Using Computer-Assisted and Conventional Techniques to Treat Patients With Extraarticular Femoral Deformities

BACKGROUND

We compared the medium-term results of total knee arthroplasty (TKA) performed using computer-assisted surgery (CAS) and conventional techniques in patients with extraarticular femoral deformities.

METHODS

The clinical and radiographic data of 40 knees (34 patients) with extraarticular femoral deformities that underwent consecutive CAS-TKA were compared with those of a control group that underwent conventional TKA (80 knees, 63 patients). No demographic data (in particular, the causes of the extraarticular deformities) differed between the two groups. The follow-up periods of the CAS and conventional TKA groups were 6.0 and 6.3 years, respectively.

RESULTS

In the CAS group, the average knee score increased from 48.2 to 89.6 at the final follow-up (P < .001); the average function score increased from 51.4 to 91.4. The range of motion averaged 105.5° preoperatively and 123.3° postoperatively. No significant differences were found in the knee score, function score, or range of motion after TKA between the 2 groups. The average preoperative mechanical axes were 18.1° varus in both groups. The average postoperative mechanical axis was 1.4° varus in the CAS group and 3.3° varus in the conventional TKA group (P = .001). The proportion of postoperatively aligned knees was 77.5% in the CAS group and 32.5% in the conventional group (P < .001).

CONCLUSION

Although the medium-term clinical results of TKA in extraarticular femoral deformities were satisfactory in both the CAS and conventional TKA groups, the former group exhibited more accurate postoperative coronal alignment. It was useful to employ navigation in patients with extraarticular deformities of various etiologies.

Preoperative Planning in Primary Total Knee Arthroplasty

Preoperative planning is of paramount importance in primary total knee arthroplasty. A thorough preoperative analysis helps the surgeon envision the operation, anticipate any potential issues, and minimize the risk of premature implant failure. Obtaining a thorough history is critical for appropriate patient selection. The physical examination should evaluate the integrity of the soft tissues, the neurovascular status, range of motion, limb deformity, and the status of the collateral ligaments to help determine the soft-tissue balancing and constraint strategy required. Standard radiographs, with a known magnification, should be obtained for preoperative total knee arthroplasty templating. Routine standing AP, lateral, and skyline radiographs of the knee can help the surgeon plan the bone cuts and tibial slope as well as the implant size and position at the time of surgery. In certain circumstances, such as severe coronal deformities, bone deficiencies, and/or extra-articular deformities, additional measures are frequently necessary to successfully reconstruct the knee. Constrained implants, metal augments, and bone graft must be part of the surgeon's armamentarium.

The difficult primary total knee arthroplasty: a review

Primary total knee arthroplasty (TKA) is a reliable procedure with reproducible long-term results. Nevertheless, there are conditions related to the type of patient or local conditions of the knee that can make it a difficult procedure. The most common scenarios that make it difficult are discussed in this review. These include patients with many previous operations and incisions, and those with severe coronal deformities, genu recurvatum, a stiff knee, extra-articular deformities and those who have previously undergone osteotomy around the knee and those with chronic dislocation of the patella. Each condition is analysed according to the characteristics of the patient, the pre-operative planning and the reported outcomes. When approaching the difficult primary TKA surgeons should use a systematic approach, which begins with the review of the existing literature for each specific clinical situation.

Accuracy of CT-based patient-specific guides for total knee arthroplasty in patients with post-traumatic osteoarthritis

Published clinical trials who studied the accuracy of patient-specific guides (PSG) for total knee arthroplasty exclude patients with articular deformity of the knee joint. We prospectively analysed a series of 30 patients with post-traumatic osteoarthritis of the knee joint with use of PSG. At 1 year post-operative, the achieved biomechanical (HKA) axis and varus/valgus of the femur and tibia components were measured on anterior-posterior (AP) long-standing weight-bearing radiographs. Flexion/extension of the femoral and AP slope of the tibia component was measured on standard lateral radiographs. Percentages >3° deviation of the pre-operative planned HKA axis and individual implant components were considered as outliers. Approved and used implant size, median blood loss (ml) and operation time (min) were obtained from the operation records. Pre- and 1-year post-operative patient-reported outcome measures (PROMs) were performed. Eighty-three per cent of the patients had a HKA axis restored <3° of the pre-operative planned alignment. Varus/valgus outliers were 0.0 and 6.7 % for the femoral and tibial components, respectively. Percentages of outliers of flexion/extension were 36.7 % for the femoral component and 10.0 % for the AP slope of the tibial component. Median blood loss was 300 ml (50-700), while operation time was 67 min (44-144). In 20 % of all cases, the approved implant size was changed into one size smaller. One-year post-operative PROMs improved significantly. We conclude that the accuracy of CT-based PSG is not impaired in patients with post-traumatic osteoarthritis and this modality can restore biomechanical limb alignment.

Comparison of Postoperative Alignment of Total Knee Replacement Using Computer-Assisted Navigation with Conventional Guiding System in Chinese Population with Significant Coronal Femoral Bowing

Background/Purpose

Coronal femoral bowing is common in Chinese population. This might affect the restoration of mechanical alignment in conventional total knee replacement (TKR). The aim of the study was to compare the postoperative alignment of conventional TKR with computer-assisted navigation TKR (CAN-TKR), to investigate the effect of femoral bowing on postoperative alignment in conventional TKR and to understand the role of CAN-TKR in limbs with significant femoral bowing.

Methods

This is a retrospective study of 331 knees that underwent TKR (either conventional or CAN-TKR) in our centre from January 2010 to June 2012. The incidence of coronal femoral bowing was measured. The postoperative alignments were compared between the two groups.

Results

The incidence of excessive coronal femoral bowing was 41.4%. For patients with or without significant coronal femoral bowing, the CAN-TKR group was significantly better in restoring postoperative mechanical axis and the coronal femoral angle (p < 0.05). Proportions of outliers were also much less in the CAN-TKR group.

Conclusion

CAN-TKR reduces outliers in all patients, and is especially superior in restoring mechanical alignments in patients with significant coronal femoral bowing.

[Computer-assisted systems in total knee arthroplasty. Useful aid or only additional costs]

BACKGROUND

The primary goal of computer-assisted surgery (CAS) in total knee arthroplasty is to increase the accuracy in terms of prosthesis positioning. In theory, this would lead to longer implant survival and a reduction of malpositioning. Thus, a better clinical outcome and lower revision rates would be expected. However, the necessary technical equipment represents significant additional effort and cost factors which are not included in the current diagnosis-related groups (DRG) system.

OBJECTIVE

The objective of this article is a critical review of the current literature to examine whether these costs are reasonable by taking the additional benefits of the technology into account.

METHODS

This review is based on a selective PubMed search on CAS and navigation in primary total knee arthroplasty.

RESULTS

The current evidence base on CAS suggests that at least the primary outcome parameter, the improvement of the radiological alignment, is achieved by the technique. However, the claimed secondary effects are not yet proven. In particular, an improvement of clinical outcome and patient satisfaction has not been demonstrated so far. Furthermore, there is some evidence of increased complication rates by the use of CAS.

CONCLUSION

Against this background and with respect to further cost-benefit analyses, the technology has to be reviewed critically. In particular, low-volume units do not seem to benefit from the use of CAS. However, the assessment of long-term effects is still pending.

Toe-out angle changes after total knee arthroplasty in patients with varus knee osteoarthritis

PURPOSE

Toeing-out is a commonly proposed kinematic variable that has been suggested to reduce external knee adduction moment. Analyses of the toe-out angle after total knee arthroplasty (TKA) are useful for obtaining a proper understanding of the abnormal gait caused by varus knee osteoarthritis (OA), as well as performing rehabilitation after arthroplasty. Changes in the toe-out angle after arthroplasty have not yet been defined or analysed.

METHODS

The study population consisted of 32 knees in 32 patients with varus knee OA who underwent TKA. The femorotibial angle was evaluated on standing anteroposterior radiographs before and after arthroplasty. The subjects underwent three-dimensional motion capture analyses to measure gait parameters (walking speed, cadence, stride length, step length, step width and the relative length of the single-limb support (SLS) percentage of one gait cycle) and the maximal hip adduction angle in the stance phase, the trunk lean angle in the coronal plane and the toe-out angle before and 4 weeks after arthroplasty.

RESULTS

The femorotibial angle on the side of arthroplasty improved after surgery. Among the measured gait parameters, only the SLS percentage increased significantly. The hip adduction angle and toe-out angle on the side of arthroplasty increased significantly after surgery.

CONCLUSIONS

The knee alignment and hip adduction angle in the coronal plane and SLS phase were normalized after arthroplasty. The increase in the toe-out angle after arthroplasty may be attributable to the restoration of a normal knee alignment. These findings contribute to obtaining a proper understanding of the abnormal gait caused by varus knee OA and are useful for orthopaedic surgeons and rehabilitation therapists when treating patients after arthroplasty.

LEVEL OF EVIDENCE

Prospective study, Level II.

The dorsal pedis artery as a new distal landmark for extramedullary tibial alignment in total knee arthroplasty

PURPOSE

It is better to use multiple anatomical landmarks to reduce errors in component alignment in total knee arthroplasty. Therefore, it is worthwhile to find a new landmark that can be used as an addition to conventional ones. Herein, we assessed the dorsal pedis artery as a new distal landmark for extramedullary tibial alignment.

METHODS

Fifty-two ankles in patients undergoing total knee arthroplasty and 10 ankles in normal controls were included. Color Doppler ultrasonography was used to locate the dorsal pedis artery at the level of the ankle joint. Conventional landmarks, including the tibialis anterior tendon, the extensor hallucis longus tendon, the extensor digitorum longus tendon, and the malleolar centre, were also located on ultrasound images. The distances between the ankle centre and each landmark were measured and compared.

RESULTS

The dorsal pedis artery was absent in 2 patients and impalpable but visible with ultrasonography in other 2 patients. The dorsal pedis artery was located anatomically closest to the ankle centre in patients (0.4 ± 3.4 mm lateral). Statistical analysis showed that the dorsal pedis artery, the extensor hallucis longus tendon, and the malleolar centre were located significantly closer to the ankle centre comparing with the extensor digitorum longus tendon and the tibialis anterior tendon in both patients and controls (p < 0.001).

CONCLUSIONS

As long as the dorsal pedis artery exists, it can be used as an addition to the conventional landmarks in total knee arthroplasty. Using this new landmark will help reduce errors in coronal plane alignment of tibial component.

LEVEL OF EVIDENCE

II.

Total knee arthroplasty with patient-specific instruments improves function and restores limb alignment in patients with extra-articular deformity

BACKGROUND

Restoring function and alignment when treating knee arthritis with a total knee arthroplasty (TKA) in patients who have an extra-articular deformity (EAD) from a malunion or with retained femoral hardware is a challenge. The normal anatomical landmarks are hard to find and difficult to use to obtain correct alignment. The procedure will be further challenged by angular deformity of the femur or tibia. A retrospective study was performed on a case series of patients with EAD or obliteration of the canal treated with patient-specific instruments (PSI).

METHODS

A multicenter retrospective review of 10 patients with multiplanar deformities in which the knee components were aligned with patient-specific instruments was performed. Outcome and alignment were studied.

RESULTS

At a mean follow-up of 3.4years, function improved from preoperative as evidenced by a mean increase in the KS pain score of 53 points, KS function score of 48 points and Oxford Score of 28 points (P<0.05). Flexion improved from 94° +/- 11° to 112° +/- 15° (P<0.05). Limb alignment was restored with a mean Hip-Knee-Ankle angle of 179.3° +/- 1.3° (P<0.05). Maximum outliers were 177° to 181°. An average tourniquet time of 75 +/- 9minutes (range, 62-83min) was observed.

CONCLUSIONS

The use of patient-specific instrumentation systems to perform TKA in patients without access to the intramedullary canal because of EAD or fixation devices, improved function and restored limb alignment. Mechanical alignment can easily be obtained with this technique by intra-articular correction of deformities under 20°.

LEVEL OF EVIDENCE

Level IV.

Easy identification of mechanical axis during total knee arthroplasty

PURPOSE

We devised an intraoperatively identifiable mechanical axis (IIMA) as a reference of alignment in total knee arthroplasty (TKA).

MATERIALS AND METHODS

Between February 2010 and January 2011, primary TKAs were consecutively performed on 672 patients (1007 knees) using an IIMA as a reference in the coronal plane.

RESULTS

The alignment of the lower extremity improved from a mean of 11.4±6.7° (-10.3-34.4°) of varus preop. to 0.7±3.5° (-5.2-8.6°) immediately after surgery. Mean alignment of the femoral component in the coronal plane was 89.3±2.3° (83.4-97.2°) postop. and mean alignment of the tibial component was 90.4±2.2° (85.1-94.2°) postop.

CONCLUSION

This study showed that IIMA could be of considerable value as a new guider of alignment that is easily accessible and highly effective during total knee arthroplasty.

Evaluation of the accuracy of a patient-specific instrumentation by navigation

PURPOSE

The aim of this study is to evaluate the accuracy of a patient-specific instrumentation (PSI) as assessed by the intraoperative use of knee navigation software during the surgical procedure.

METHODS

Fifteen patients with primary gonarthrosis were selected for unilateral total knee arthroplasty. The first three patients were excluded from this study, as they were considered to be a warm up to set-up the procedure. All patients were operated on with a cemented posterior-stabilised prosthesis cruciate ligament-sacrificing by the same surgeon using the patient matched cutting jigs. The size of the implant, level of resection, and alignment in the coronal and sagittal planes were evaluated. An unsatisfactory result was considered an error ≥2° in both planes for each component as a possible error of 4° could result in aggravation.

RESULTS

On the coronal plane the mean deviation of the tibial guide from the ideal alignment was 1.2 ± 1.5 (range 0-5°) and in the sagittal plane was 3.8 ± 2.4 (range 0-7.5°). On the coronal plane the mean deviation of the femoral guide from the ideal alignment was 1.2 ± 0.6 and in the sagittal was 3.7 ± 2.

CONCLUSION

On the basis of this preliminary experience the PSI system based only on data acquisition with A-P radiograms and RMN cannot be defined as accurate. In cases of the use of the custom made cutting jigs it is recommended to perform an accurate control of the alignment before making the cuts, for any step of the procedure.

LEVEL OF EVIDENCE

II.

Does the severity of preoperative varus deformity influence postoperative alignment in both conventional and computer-assisted total knee arthroplasty?

PURPOSE

The postoperative alignment was compared according to the severity of preoperative varus deformity in computer-assisted and conventional total knee arthroplasty (CAS-TKA).

METHODS

The study reviewed 127 consecutive CAS-TKA and 236 conventional TKA, retrospectively. In CAS-TKA, 77 knees with a varus deformity ≤15.0° were classified in group CAS-A and 50 knees with a varus deformity >15.0° were classified in group CAS-B. In conventional groups, 204 knees with a varus deformity ≤15.0 were classified in group Conventional-A and 32 knees with a varus deformity >15.0° were classified in group Conventional-B. The postoperative mechanical axis (MA) was compared among groups CAS-A, CAS-B, Conventional-A and Conventional-B.

RESULTS

The average postoperative MA was 0.7° varus in group CAS-A, 2.8° varus in group CAS-B, 1.1° varus in group Conventional-A and 3.2° varus in group Conventional-B (p < 0.001). The postoperative MA was within 3° in 81.8, 62.0, 58.8 and 37.5 % of group CAS-A, CAS-B, Conventional-A and Conventional-B, respectively.

CONCLUSIONS

The severity of preoperative varus deformity influences postoperative alignment despite using CAS. More careful correction of the alignment is required, especially in TKA performed on patients with a greater varus deformity.

LEVEL OF EVIDENCE

III.

The accuracy of the extramedullary and intramedullary femoral alignment system in total knee arthroplasty for varus osteoarthritic knee

PURPOSE

The intramedullary (IM) femoral alignment system does not alway guarantee accuracy of the component position in the total knee arthroplasty (TKA). In some cases, the extramedullary (EM) femoral alignment system in total knee arthroplasty (TKA) is a useful alternative surgical option to adjust femoral component alignment. In the EM technique, accuracy of the femoral head center location is mandatory. The purpose of this prospective randomized study was to compare the alignment after TKA using two different femoral alignment systems.

METHODS

From January 2009 to December 2009, 91 patients (106 knees) with osteoarthritis underwent TKA. The IM femoral alignment system was used in 50 TKAs, and the EM system was used in 56 TKAs. We measured the coronal, sagittal alignment of the femoral component, and overall alignment from full-length standing. Anteroposterior radiographs were taken 1 year after surgery.

RESULTS

The overall limb alignment was 0.2° ± 1.9° varus in the EM group and 1.1° ± 1.9° valgus in the IM group (p = 0.001). The coronal alignment of the femoral component was 90.0° ± 1.1° in the EM group and 90.3° ± 1.2° in the IM group, not statistically different (n.s.). The sagittal alignment of the femoral component was 2.3° ± 1.7° in the EM group and 2.5° ± 1.0° in the IM group (n.s.). Clinically acceptable overall limb alignment was achieved in 91.1 % of EM group and 84.0 % of IM group (n.s.).

CONCLUSION

The present study suggests that by applying our EM technique that uses a newly designed mechanical axis marker system, the alignment of the femoral component and overall limb alignment is reliable and at least as accurate as the standard IM technique.

LEVEL OF EVIDENCE

I.

Computer-assisted navigation for the intraoperative assessment of lower limb alignment in high tibial osteotomy can avoid outliers compared with the conventional technique

PURPOSE

Longterm outcomes after valgization high tibial osteotomy (HTO) to treat varus osteoarthritis seem to depend mainly on correction precision. Intraoperative assessment of leg alignment based on radiological visualization of the mechanical axis is difficult and its precision is limited. A promising approach to improving precision is to make use of navigation systems. The case-control study reported here involved the evaluation of patients whose varus osteoarthritis had been treated by open-wedge high tibial ostoetomy, and an analysis of the effect of computer-guided navigation on postoperative leg alignment.

METHODS

Forty patients with medial varus osteoarthritis managed by open-wedge high tibial osteotomy using a surgical navigation system were included in the present study (Group 1). They were compared with a retrospective control group (Group 2) of 40 patients with respect to postoperative leg alignment, correlation of planned and definitive correction, and postoperative deviation from the Fujisawa point.

RESULTS

The mean values for planned and definitive correction showed no significant differences for identical demographic data. As a percentage of the width of the tibial plateau the postoperative weight-bearing radiographs showed a mechanical line that intersected with the knee base line at the desired value of 62% (Fujisawa point) in 58.8% (SD ± 6.1) in Group 1 and in 58.6% (SD ± 8.1) in Group 2. Despite similar mean values a significantly higher number of corrections were outside the reference area (n = 7) in the non-navigated group, whereby all corrections were within the desired range in the navigated group. There were no significant differences in operation time.

CONCLUSIONS

This study showed that the use of a navigation system can not increase the precision of the open-wedge HTO procedure in patients with varus osteoarthritis but it can eliminate the outliers of a well defined range.

LEVEL OF EVIDENCE

Case-control study, Retrospective comparative study, Level III.

The limits of precision in conventionally instrumented computer-navigated total knee arthroplasty

PURPOSE

Computer-navigated total knee arthroplasty (TKA) improves the accuracy of component implantation. However, the final implant alignment may not match planned alignment. The hypothesis of this study is that although computer navigation improves alignment, imprecision may not be completely eliminated. The aim of the study was to establish the incidence and sources of imprecision during TKA using computer navigation to measure deviations from planned alignment.

METHODS

Computer navigation was used to quantify changes in planned alignment at four steps during 136 TKA's: application of cutting blocks, addition of definitive pin fixation, bone cuts and after prosthesis application. Mean changes in alignment deviation at each step in each plane were measured and the number of significant outliers (>3° from the planned resection plane) were assessed in each plane.

RESULTS

Overall changes in planned alignment were small and non-cumulative between steps but the incidence of outliers (cuts measured as >3° from planned alignment at each step) increased through the steps, with 21.3 % (n = 29) of final implants outlying in the tibial sagittal plane, which was the least precise plane. The highest number of outliers occurred after bone resection and the addition of pins to cutting blocks was also identified as a source of imprecision.

CONCLUSION

Despite improved accuracy of bone resection with computer-navigated TKA, the precision of bone cuts may be affected at several steps of the procedure. Cutting block application, bone resection and prosthesis application may all affect accuracy. Bone cuts should be made with meticulous care, whether navigated or not, and navigated cuts should be checked and corrected, particularly in the tibial sagittal plane.

LEVEL OF EVIDENCE

IV.