Intramedullary Guides Research Articles

Angle Accuracy of Intramedullary Bone Resection Guides for Total Knee Arthroplasty.

The importance of proper prosthetic placement has been confirmed in numerous studies. The objective of this study was to compare the planned resection angles to the verified intraoperative angles of femoral and tibial varus/valgus, tibial slope, and femoral flexion for each total knee performed using intramedullary (IM) cut guides for both distal femur and proximal tibia cuts. A total of 1,000 total knee arthroplasties (TKAs) were evaluated for this study. Intraoperative cut-check technology was used to show real-time validation of these resection angles. Assuming an acceptable range of within 2° of the planned cuts, results show the femoral varus/valgus angles were 75% accurate, the femoral flexion angles were 50.8% accurate, the tibial cuts were 95.2% accurate in the coronal plane, and the tibial slope was the least accurate with only 50.3% within the acceptable range. This showed that IM guides are reasonably accurate in producing desired angles in the coronal plane but less accurate in the sagittal plane, with a greater number of outliers in femoral flexion and posterior slope. Surgeons need to be aware of potential cutting errors when using IM guides as they affect the overall alignment of the implant, and real-time verification technology is available to verify the accuracy of the cuts.

Robotic arm-assisted total knee arthroplasty in a patient with osteopetrosis: a case report and review of literature.

Osteopetrosis, a rare condition arising from osteoclast dysfunction, is characterised by increased bony density and obliteration of the intramedullary canal. While total knee arthroplasty (TKA) is preferred for osteoarthritic patients with osteopetrosis, inherent disease characteristics pose surgical challenges. This article presents a patient with osteopetrosis treated with robotic arm-assisted TKA (RA-TKA). This approach provided precise bone resection, obviates the need for intramedullary guides, minimizes saw disposal, and reduces surgical duration, with satisfactory short-term outcomes. RA-TKA may be an effective treatment for osteoarthritis in patients with osteopetrosis.

Spacer Block Technique Was Superior to Intramedullary Guide Technique in Coronal Alignment of Femoral Component after Fixed-Bearing Medial Unicompartmental Knee Arthroplasty: A Case-Control Study.

Backgrounds and Objectives: The spacer block technique in unicompartmental knee arthroplasty (UKA) has still a concern related to the precise position of the component in the coronal and sagittal planes compared to intramedullary guide technique. The purposes of this study were to explore whether the spacer block technique would improve the radiological alignment of implants and clinical outcomes compared with the outcomes of the intramedullary guide technique in fixed-bearing medial UKA. Materials and Methods: In total, 115 patients who underwent unilateral, fixed-bearing medial UKA were retrospectively reviewed and divided into group IM (intramedullary guides; n = 39) and group SB (spacer blocks; n = 76). Clinical assessment included range-of-motion and patient-reported outcomes. Radiological assessment included the mechanical femorotibial angle, coronal and sagittal alignments of the femoral and tibial components, and coronal femorotibial congruence angle. Results: All clinical outcomes showed no significant differences between groups. The coronal femoral component angle was valgus 2.4° ± 4.9° in IM group and varus 1.1° ± 3.2° (p < 0.001). In group IM, the number of outlier in coronal femoral component angle (<−10° or 10°<) was 3 cases, while in group SB, there was no outlier (p = 0.014). The coronal femorotibial congruence angle was significantly less in group SB (mean 1.9°, range, −3.2°~8.2°) than in group IM (mean 3.4°, range, −9.6°~16.5°) (p = 0.028). Conclusions: In the group SB, the coronal alignment of femoral component was closer to neutral, and outlier was less frequent than in the group IM. The spacer block technique was more beneficial in achieving proper coronal alignment of the femoral component and congruence of femorotibial components compared to the intramedullary guide technique in fixed-bearing medial UKAs.

Treatment Approach for Knee Osteoarthritis with Ipsilateral Femoral Cartilage Tumor: A Case Series

Osteoarthritis (OA) is a common pathology affecting the knee joint. Twenty percent of the cartilaginous tumors of bone are in the distal femur. This presents a challenge for treating patients with knee OA who also have ipsilateral distal femur cartilage tumors. We propose a classification system for knee OA with ipsilateral cartilaginous tumor and a treatment approach to address this issue. Intramedullary guides are avoided when performing total knee arthroplasty (TKA) in these patients so as not to further contaminate the femur with tumor cells. A non-image-based stereotactic surgical system is favored at our institution to achieve this goal. Seven patients underwent classification and treatment with TKA utilizing this approach. Average final follow-up was 15.3 months. Component alignment averaged 89.2° and all patients had 0° of extension with an average flexion to 107.5°. There were no postoperative complications and no radiographic evidence of component complication, tumor recurrence, or tumor expansion. Few studies have reported on the treatment of knee OA with concurrent cartilaginous tumor of the distal femur. All patients treated with the proposed approach had their OA successfully treated without complication related to their cartilaginous tumor or TKA components. This case series presents a novel classification and treatment algorithm to potentially guide arthroplasty surgeons in approaching these often-concurrent occurring pathologies.

A Flexible Intramedullary Guide Can Reduce the Anteroposterior Oversizing of Femoral Components Used in Total Knee Arthroplasty in Patients with Osteoarthritis and Severe Distal Femoral Sagittal Bowing.

Traditionally, a rigid intramedullary rod has been used as the reference guide for femoral cutting in total knee arthroplasty (TKA). However, correct positioning of this rigid rod is difficult, especially in the knees with severe distal femoral sagittal bowing. A flexible intramedullary rod has been developed to address this problem. This study was performed to compare the sagittal alignment and clinical outcomes of TKAs performed with flexible and rigid femoral intramedullary guides. Thirty-eight knees that underwent primary TKAs with flexible intramedullary rods as femoral cutting guides were matched according to patient height and sex with 38 knees that underwent TKAs using conventional rigid rods. Clinical outcomes, including the range of motion and functional scores, and radiological variables, including the distal femoral bowing angle (DFBA), femoral component flexion angle (FFA), and mediolateral overhang and anteroposterior (AP) oversizing of femoral components, were evaluated. Clinical and radiological outcomes did not differ significantly between the flexible rod and conventional rigid rod groups. A subgroup analysis of knees with severe distal femoral sagittal bowing (DFBA >4 degrees) showed that the FFA was significantly larger in the flexible rod group than in the rigid rod group, with an average difference of 3 degrees (5.2 ± 2.4 vs. 2.2 ± 1.6 degrees, respectively, p = 0.022). In addition, the incidence of AP oversizing of femoral components was lower in the flexible rod group than in the rigid rod group (11.1 vs. 60.0%, respectively, p = 0.027). Relative to TKA with a rigid rod, TKA performed with a flexible femoral intramedullary guide resulted in more flexed sagittal alignment of femoral components in patients with severe distal femoral sagittal bowing. This greater flexion of the femoral component resulted in less AP oversizing. However, the use of a flexible rod had no impact on short-term clinical outcomes.

Computer navigation does not improve 10-year functional outcomes following total knee arthroplasty: A randomised clinical trial

Purpose: The use of computer-assisted surgery (CAS) in total knee arthroplasty (TKA) has been widely shown to be beneficial in improving prostheses alignment. The evidence of correlation to superior functional result, however is both sparse and conflicting. Methods: TKA participants were randomised into one of three trial arms to compare implantation techniques; CAS, intramedullary instrumentation guides for femur and tibia or intramedullary guides for femur and extramedullary tibial jigs. This was a single centre trial, with one senior surgeon performing all surgeries through a standardised medial parapatellar approach and cemented prostheses. Participants were blinded to surgical technique, and post-operatively followed up for 10 years. Outcome measures included a Numerical Knee Pain Rating, Oxford Knee Score and Short Form Health Survey and Likert satisfaction score. Results: 107 patients were successfully randomised for age, body mass index and knee function. Mean surgical times were 112 minutes for CAS, 82 minutes for EM/IM and 79 minutes for IM/IM. 68 patients completed 10-year follow-up. We failed to find significant differences in knee pain (p=0.11), knee function (p=0.24), satisfaction (p=0.43) or health status physical component score (p=0.06) or mental component score (p=0.29) at 10 years. Conclusion: 10-year results of this study indicate that compared to conventional techniques, CAS fails to provide superior long-term functional outcomes for patients undergoing TKA.

Systematic Review of Accelerometer Based Navigation in Total Knee Arthroplasty: Improved Alignment, Clinical Results, and Patient Reported Outcomes Compared to Conventional Guides?

Background: There have been significant advancements to restore knee alignment postoperatively in the TKA population. This includes the use of accelerometer-based portable navigation (ABN). ABN can lead to a more precise restoration of the neutral mechanical axis, improve efficiency and potentially decrease early- and long-term complications. The degree with which ABN can achieve this remains unclear. We performed a systematic review to answer this question. Methods: We performed a systematic review in accordance with Cochrane guidelines of controlled studies (prospective and retrospective) in MEDLINE with an emphasis on studies comparing postoperative outcomes such as mechanical axis alignment, operative time, blood loss, complications and clinical outcome scores in total knee arthroplasty patients using ABN versus conventional intramedullary guides. Results: ABN was associated with significantly fewer outliers in hip-knee-ankle alignment (p = 0.0006), femoral component alignment (p &lt; 0.0001). ABN was associated with significantly less estimated blood loss (p = 0.05) and no difference in operative times (p = 0.21). Finally, there was no difference regarding functional outcomes or DVT. Conclusion: ABN more accurately achieves neutral mechanical alignment with a smaller incidence of outliers. There was not an increase in operative time with using ABN and there were reductions in blood loss as well. We conclude that ABN offers the benefit of improved mechanical alignment.

Does the sequential addition of accelerometer-based navigation and sensor-guided ligament balancing improve outcomes in TKA?

A significant percentage of patients remain dissatisfied after total knee arthroplasty (TKA). The aim of this study was to determine whether the sequential addition of accelerometer-based navigation for femoral component preparation and sensor-guided ligament balancing improved complication rates, radiological alignment, or patient-reported outcomes (PROMs) compared with a historical control group using conventional instrumentation. This retrospective cohort study included 371 TKAs performed by a single surgeon sequentially. A historical control group, with the use of intramedullary guides for distal femoral resection and surgeon-guided ligament balancing, was compared with a group using accelerometer-based navigation for distal femoral resection and surgeon-guided balancing (group 1), and one using navigated femoral resection and sensor-guided balancing (group 2). Primary outcome measures were Patient-Reported Outcomes Measurement Information System (PROMIS) and Knee injury and Osteoarthritis Outcome (KOOS) scores measured preoperatively and at six weeks and 12 months postoperatively. The position of the components and the mechanical axis of the limb were measured postoperatively. The postoperative range of motion (ROM), haematocrit change, and complications were also recorded. There were 194 patients in the control group, 103 in group 1, and 74 in group 2. There were no significant differences in baseline demographics between the groups. Patients in group 2 had significantly higher baseline mental health subscores than control and group 1 patients (53.2 vs 50.2 vs 50.2, p = 0.041). There were no significant differences in any PROMs at six weeks or 12 months postoperatively (p > 0.05). There was no difference in the rate of manipulation under anaesthesia (MUA), complication rates, postoperative ROM, or blood loss. There were fewer mechanical axis outliers in groups 1 and 2 (25.2%, 14.9% respectively) versus control (28.4%), but this was not statistically significant (p = 0.10). The sequential addition of navigation of the distal femoral cut and sensor-guided ligament balancing did not improve short-term PROMs, radiological outcomes, or complication rates compared with conventional techniques. The costs of these added technologies may not be justified. Cite this article: Bone Joint J 2020;102-B(6 Supple A):24-30.

Accuracy of a Novel 3D‐Printed Patient‐Specific Intramedullary Guide to Control Femoral Component Rotation in Total Knee Arthroplasty

ObjectiveTotal knee arthroplasty (TKA) is one of the most universal and effective means for treating terminal stage osteoarthritis (OA) of knee. Accurate intramedullary guide of femur is the basis for the distal femoral cuts. Determining the surgical transepicondylar axis (sTEA) is the key to reconstruction of the femoral rotational alignment, because the correct rotational alignment can place the femoral component in the right position, balance the flexion gap so that the inner and outer tension is equal, get stability during the flexion process of the knee, and enhance the quality of life of patients. With the development of three‐dimensional printing (3DP) technology in the medical domain, the application of patient‐specific instrumentation (PSI) in arthroplasty has become more common. The aim of this study was to evaluate the accuracy of a novel 3D‐printed patient‐specific intramedullary guide to control femoral component rotation in TKA.MethodsEighty patients (65 females and 15 males) with knee OA were included in this prospective randomized study. The patients were divided into two groups by random number table method, 40 in each group. TKA assisted by PSI (PSI group) and conventional TKA (conventional group) was performed respectively. Clinical outcomes [operation time, postoperative drainage volume, duration of drainage, Hospital for Special Surgery knee score (HSS), American Knee Society knee score (AKS)] and radiological outcomes [hip‐knee‐ankle angle (HKA), posterior condylar angle (PCA), patella transverse axis‐femoral transepicondylar axis angle (PFA), depth of intramedullary guide] were compared between and within the two groups.ResultsPSI group had less postoperative drainage volume but longer operation time than the conventional group (P < 0.05). The AKS and HSS scores after surgery were improved compared with those before surgery in each group (P < 0.05). However, there was no significant difference in the duration of drainage and range of motion (ROM) after surgery between the two groups. For the radiological results, the HKA and PFA were improved after surgery in both groups (P < 0.05).The postoperative PFA and PCA of the PSI group were closer to 0°, which was better than that of the conventional group (P < 0.05). The depth of intramedullary guide in the PSI group was less than the conventional group (P < 0.05). But there was no significant difference in HKA before and after surgery between the two groups as well as the preoperative PFA.ConclusionThe short‐term clinical efficacy of TKA assisted by PSI was similar to the conventional TKA. Although TKA assisted by PSI spent more time during operation, it could assist in intramedullary guide and align femoral rotation more accurately.

Angular limit for coronal joint deformity correction using intramedullary guidance in total knee arthroplasty. A pilot study.

Introduction: Post-operative misalignment of the lower limb mechanical axis following total knee arthroplasty (TKA) is thought to be associated with clinical failure. In a balanced knee, a neutral global mechanical axis following the use of intra-medullary (IM) guidance does not necessarily imply a horizontal TKA joint line. Using femoral and tibial axes separately would be more accurate in evaluating TKA alignment. Thus, the aim of the study is to define a pre-operative mechanical tibial and/or femoral angle threshold value for post-operative optimal alignment correction using IM guides. Methods: This single-center prospective continuous pilot study included 50 patients treated with a TKA for primitive osteoarthritis. Femoral and tibial cuts were performed using intramedullary (IM) guide. Three angles were calculated and analyzed pre and post-operatively on standing antero-posterior views using long-leg radiographs: femorotibial angle (FTA), mechanical femoral angle (MFA), and mechanical tibial angle (MTA). Statistical analysis was performed for the whole sample and for the three following FTA subgroups; normo-axial, varus and valgus. Results: The pre-operative MTA is the only parameter for which a threshold value was observed; when pre-operative MTA exceeded the value of 94°, an optimal correction might not be obtained post-operatively. Discussion: Our results suggest that the bony correction obtained via IM guiding depends exclusively on the primary deformation of the tibia. In cases of a varus of more than 94°, the IM guide was found to yield sub-optimal corrections. Thus, other solutions need to be investigated.

Accelerometer-Based Navigation in Total Knee Arthroplasty for the Management of Extra-Articular Deformity and Retained Femoral Hardware: Analysis of Component Alignment.

Purpose Recent advances in total knee arthroplasty (TKA) include an accelerometer portable system designed to improve component position and alignment. The purpose of this study is to evaluate whether accelerometer navigation system can be a valuable option in complex TKAs for extra-articular deformity of the lower limb or in case of retained femoral hardware. Methods A group of 13 patients underwent TKA with an accelerometer navigation system. Three patients had a tibial extra-articular deformity, six had a femoral extra-articular deformity, and four had an intramedullary nail in the femur. Preoperative and postoperative mechanical axes were measured from full-length lower extremity radiographs to evaluate alignment. The alignment of prosthetic components in the frontal and sagittal planes was determined by postoperative radiographs. Results At 30-days postoperative radiographic check, the hip knee ankle angle was within 2.0° (0 ± 1) of the neutral mechanical axis. The alignment of the tibial component on the frontal plane was 90.0° (range 89–91) and on the sagittal plane 5.0° (range 3–7). The alignment of the femoral component on the frontal plane was 90.0° (range 89–91) and on the sagittal plane 3.0° (range 0–5). Conclusion The alignment of the prosthetic components has been accurate and comparable to other navigation systems in literature without any increase in surgical times. The accelerometer-based navigation system is therefore a useful technique that can be used to optimize TKA alignment in patients with extra-articular deformity or with lower limb hardware, where the intramedullary guides cannot be applied. Level of Evidence This is an observational study without a control group, Level III.

An accelerometer-based navigation did not improve the femoral component positioning compared to a modified conventional technique of pre-operatively planned placement of intramedullary rod in total knee arthroplasty.

Although the most commonly used method of femoral component alignment in total knee arthroplasty (TKA) is intramedullary (IM) guides, this method demonstrated a limited degree of accuracy. Because of the femoral anterior bowing, the tip of the guide rod will impinge on the anterior cortex if a long rod is inserted. We hypothesized that the pre-operative planned insertion depth of the rod could increase the accuracy of the femoral component positioning in conventional TKA (modified conventional technique). Accelerometer-based, portable navigation device has been postulated to have better accuracy than conventional TKA in component positioning. The purpose of this study was to compare the post-operative femoral component alignment of TKA using the modified conventional technique with the accelerometer-based navigation. Fifty-five knees underwent TKA using the modified conventional technique and femoral component positioning was compared with 55 knees performed using the accelerometer-based navigation device. The femoral component alignment was evaluated with a CT-based three-dimensional software. The mean absolute deviation from targeted alignment in the sagittal plane was significantly less in the modified conventional cohort than in the accelerometer-based navigation cohort (1.1° vs 2.6°, P < 0.001). In the modified conventional cohort, 96.4% had an alignment within 3° of a targeted angle in the coronal plane (vs 89.1% with the accelerometer-based navigation, P = 0.14), and 96.4% in the sagittal plane (vs 74.5% with the accelerometer-based navigation, P < 0.001). The modified conventional technique is a simple and equal to or more accurate method than the accelerometer-based navigation in positioning the femoral component in TKA at a mid-volume hospital.

Computer-assisted surgery in total knee replacement: advantages, surgical procedure and review of the literature.

Introduction: Total knee replacement (TKR) is one of the most frequent orthopaedic procedures performed every year. At the same time 20% of patients who underwent TKR are not satisfied with the outcome. The reasons are unknown; we think that a mechanical alignment beyond 3° of varus-valgus can represent the most important cause of failure of TKR and consequently patient dissatisfaction. Materials and Methods: Neutral mechanical alignment is the main goal in every TKR: this can be achieved through different tools, such as extramedullary and intramedullary guides, patient-specific instrumentation (PSI) and computer-assisted surgery (CAS). The aim of this review is to compare the different alignment techniques in TKR, to describe CAS procedure and CAS results in recent literature. Results: Regarding the intramedullary guide, there is an increased risk of fatty embolism; there are great limitations on its use, or even impossibility, in cases of bone deformity and sequelae of trauma. Regarding the extramedullary guide, it becomes more difficult to use in cases of great obesity or increased soft-tissue volume around the tibia. PSI for TKR has been introduced to improve alignment, reduce outliers, operation time and the risk of fatty embolism by avoidance of intramedullary canal violation. Recent randomized controlled trials and meta-analysis proved no advantage of PSI in improving mechanical axis and implant survivorship. Discussion: CAS has provided to be a useful tool in assisting the surgeon to achieve more accurate post-operative mechanical axis through precise and reproducible bone cuts and ligament balancing. Two meta-analyses definitively proved that CAS technique improves mechanical axis and implant survivorship and one recent meta-analysis demonstrated that CAS provides better mechanical alignment and higher functional scores at short-term follow-up. (www.actabiomedica.it)

Hospital-based Patient-specific Templates for Total Knee Arthroplasty: A Proof of Concept Clinical Study.

Introduction:All available patient-specific instruments or patient-specific templates (PSTs) are controlled by implant companies. Most of these companies outsource some of the steps of the PST such as imaging, preoperative planning, manufacturing of PST, and packing/sterilization. This is a proof of concept clinical study on the hospital-based PST system for total knee arthroplasty (TKA).Methods:A total number of 257 TKA procedures were performed on the basis of a new concept of hospital-based PSTs. All 5 steps of the PST [ie, imaging (computed tomographic scanning), planning, PST production, packing/sterilization, and surgery] were performed by the hospital. All cases included in this work are documented in the Egyptian Community Arthroplasty Register.Results:All cases had their surgeries performed without resorting to conventional intramedullary guides. Computed tomography–based imaging was easy and affordable. Planning was controlled by the surgeon. Polyamide nylon was the best available material and it was autoclavable. Desktop 3-dimensional printers were able to produce PSTs made of nylon, but it was difficult and time consuming. Industrial printers were superior in quality to desktop printers but more expensive. The whole process could be performed in as short a duration as 3 working days.Conclusions:Hospital-based PST was feasible and it was facilitated by the introduction of desktop 3-dimensional printers. This technique was less expensive and more time saving than commercially available PSTs as well as the conventional TKA.

3D PRINTING TECHNIQUE FOR PATIENT-SPECIFIC INSTRUMENTATION IN TOTAL KNEE ARTHROPLASTY

The aim of the study was to evaluate clinical and radiological outcomes of knee arthroplasty using patient specific guides produced using physical prototypes and 3D printing that are applied for positioning of resection blocks. Materials and methods. The authors analyzed the treatment outcomes of 4 patients during the period from 2015 to 2016 who underwent total knee arthroplasty for posttraumatic gonarthrosis of III-IV stage with the use of patient specific guides for resection blocks positioning. The mean age of patients was 59±12 years. Initially, all patients reported marked limitation of movement in the knee joint. The average flexion prior to surgery was 53.3±35.1°. According to FLFS roentgenography all patients had a varus deformity of the lower limb with an average value of 15.0±12.3°.Results. In all cases the axis of the lower limb was normalized postoperatively. The average KOOS score for “pain” was 85.2±14.0, for “daily physical activity” — 74.5±14.8, for “symptoms and stiffness” — 69.0±11.0, for “quality of life” — 62.5±12.5 points. Average knee ROM after arthroplasty: flexion 113.3±5.787° and full extension. Such outcomes can be considered as excellent considering preoperative marked knee movement limitations in all patients.Conclusion. Preoperative planning using the technology of producing patient specific guides and prototyping on physical tibia and femur models allowed to restore normal axis of the lower limb. The authors observed a significant improvement in joint function and a pain syndrome reduction in all patients. In authors’ opinion patient specific precision guides can be used in the following cases: inflammatory process or deformation of the femur in patient’s history; when the use of intramedullary guides is difficult and does not allow positioning of the prosthesis components with sufficient accuracy or is associated with an increased risk of a purulent-inflammatory process; ipsilateral hip joint prosthesis when it is desirable to avoid opening the medullary canal; substantial bone defects or massive osteophytes of the posterior portion of femoral condyles that impede correct rotation of the femoral component; severe movement limitations in the knee joint, when it is technically impossible to perform TKA using computer navigation and the use of a standard set of instruments poses significant technical difficulties.

Use of Shorter Intramedullary Guide for Ipsilateral Total Knee Arthroplasty following Prior Total Hip Arthroplasty.

Alignment after total knee arthroplasty (TKA) plays an important role with respect to patient satisfaction and implant survivorship. In patients undergoing ipsilateral TKA with prior total hip arthroplasty (THA), the femoral intramedullary (IM) guide cannot be fully inserted into the femoral canal because of the prior THA. The purpose of this study was to determine the effect of femoral component alignment using a shorter IM guide during TKA in patients with an ipsilateral THA. We identified 42 patients undergoing ipsilateral TKA with the use of a short IM guide in the setting of a prior THA. A matched cohort group was identified from our total joint registry that included 42 patients who underwent primary TKA. The surgical goal was to achieve 5 degrees of valgus on the femoral side and 0 degree on the tibial side with an overall postoperative tibial-femoral angle of 5 degrees of valgus. Patients were evaluated clinically using Knee Society pain scores (KSSs), function scores, and with radiography. Both the tibial-femoral limb alignment and the femoral component alignment were compared using Student's t-test. There were no significant differences between the two groups with respect to sex, age, body mass index (BMI), pre- and postoperative KSSs. There was a statistically significant difference between the two groups with respect to radiographic tibial-femoral limb alignment, 4.33 degrees of valgus in the short stem THA-TKA group versus 5.4 degrees of valgus in the TKA group (p < 0.04); however, this difference did not correlate to a difference in postoperative outcomes. An adequate tibial-femoral component alignment was achieved in patients undergoing ipsilateral TKA with prior THA using a shortened IM femoral guide.

Evaluation of lower limb axial alignment using digital radiography stitched films in pre-operative planning for total knee replacement

BackgroundFor patients with knee osteoarthritis, even slight anatomical variations in the femur or the tibia could affect total limb alignment during total knee replacement (TKR). Our hypothesis implies that the femoral valgus correction angle (VCA) in patients indicated for TKR, is variable and higher than the reported norm of 6° utilized in most intramedullary instrumentation systems, and that tibial bowing may result to a disparity of the tibial mechanical axis to the anatomical axis. MethodsOur study is a retrospective review of 216 pre-operative arthritic knees, which investigated the lower limb axial alignment using digitally-stitched films. Patients excluded from the study are those with history of previous tibial or femoral osteotomy, secondary gonarthrosis, rheumatoid arthritis, previous femoral or tibial fracture, patients for bilateral TKR, or history of hip surgery. ResultsThe mean age was 68-years old (range 39–86 years). The mean VCA was 7° (4.7–9.3) for men and 6.6° (4.9–9) for women. However, 71 patients (33%) had more than 7° VCA. Subsequently, 46 patients (21%) had tibial bowing producing an angle >1.5° between its mechanical and anatomic axis. ConclusionsThe 6° standard when used as a guide may result in suboptimal prosthesis positioning during conventional TKR surgery. Therefore our findings suggest that the femoral valgus correction angle has a broad range, and using standard femoral intramedullary guides should not be overlooked.

What is the optimal valgus pre-set for intramedullary femoral alignment rods in total knee arthroplasty?

In total knee arthroplasty (TKA), intramedullary guides are often used for aligning the distal femoral cutting block. Because of the highly varying angles between the mechanical axis and the anatomical femoral axis (AMA), different valgus pre-sets have been recommended. The present study investigated the optimal valgus pre-set (measuring the AMA in long-leg radiographs or at 5°, 6°, 7° or 8° valgus) to align the cutting block perpendicularly to the mechanical axis. The AMA was preoperatively measured in weight-bearing long-leg radiographs. After alignment of the cutting block by means of an intramedullary rod, deviation of the block from the mechanical femoral axis was measured with a pinless navigation device. The true AMA (tAMA) was calculated by adding the valgus pre-set of the alignment rod to the deviation measured with the navigation device. Mean deviations between the tAMA and (a) the AMA measured by the surgeon, (b) the AMA calculated with the computer software, (c) 5°, (d) 6°, (e) 7° and (f) 8° valgus pre-sets were measured for each patient. The lowest mean differences were determined. The 40 knees measured showed a mean tAMA of 7.2° valgus (1.7 SD) (range 4°-11.5°). The following mean differences and 95% limits of agreement were calculated: 2.2 (-1.2, 5.5) to the tAMA for the 5° valgus pre-set, 1.2 (-2.2, 4.5) for 6°, 0.2 (-3.2, 3.5) for 7° and -0.8 (-4.2, 2.5) for 8°. AMA measurements by the surgeon and with the digital medical planning software yielded mean differences of 0.6 (-3.1, 4.3) and 0.4 (-4.1, 4.8), respectively. In the present setting, the best mean distal femoral cutting block alignment perpendicular to the mechanical femoral axis could be achieved with a valgus pre-set of 7° and not by measuring the AMA. Nevertheless, we recommend conducting weight-bearing radiographs of the entire leg prior to TKA for easy detection of any anatomical varieties, old fractures, long stems of total hip arthroplasties or cement. However, surgeons must be aware that exact coronal component alignment can only be achieved by navigational devices. Diagnostic study, Level II.

Patient specific instrumentation in total knee arthroplasty: a state of the art.

Patient specific instrumentation (PSI) is a modern technique in total knee arthroplasty (TKA) aiming to facilitate the implant of the prosthesis. The customized cutting blocks of the PSI are generated from pre-operative three-dimensional model, using computed tomography (CT) or magnetic resonance imaging (MRI). A correct surgical plan is mandatory for a good surgical implant. The PSI guide takes into account any slight deformities or osteophytes and applies preoperative planning for bone resection, using the pre-determined implant size, position, and rotation. The apparent benefits of this technology are that neutral postoperative alignment is more reproducible, surgical time is decreased, and the entire procedure results more efficient and cost-effective. The use of PSI is indicated when advanced osteoarthritis, severe pain, and limited function/walking ability are present, such as in a standard instrumentation TKA. In addition to that, PSI finds its indication when intra-medullary guides cannot be used. For example, when there is a post-traumatic femoral deformity. Large debates have taken place about this topic during the last years and, at the moment, there is no consensus in literature regarding the accuracy and reliability of PSI as many studies have shown controversial and inconsistent results. Literature does not suggest PSI techniques as a gold standard in TKA, and therefore it cannot be recommended as a standard technique in standard, not complicated primary TKA. Moreover, literature does not underline any improvement in components alignment, surgical time, blood loss or functional outcomes. Nevertheless, many patients who underwent TKA suffered a previous trauma. In case of deformities, like femoral or tibial fractures healed with a malalignment, preoperative planning may result difficult, and some intra-operative technical difficulties can occur, such as the use of intra-medullar rod. In these selected cases, PSIs may be very useful to avoid errors in alignment and planning.

Radiological Outcomes and Operative Time following Total Knee Arthroplasty using Accelerometer-based, Portable Navigation versus Conventional Inter-Medullary Alignment Guides

Objectives:Accelerometer-based, portable navigation instrumentation is a new method of achieving desired resection alignments in total knee arthroplasty (TKA).Methods:After randomisation and the application of exclusion criteria, 79 knees were analysed. 42 patients which underwent TKA using conventional intra-medullary (IM) alignment guides were compared to 37 patients with the use of accelerometer-based, portable navigation device (KneeAlign; OrthoAlign Inc, Aliso Viejo, California). Radiographic results were obtained from post-operative computer-tomography following the CT Perth Protocol.Results:In the IM cohort, 81.0% of patients had a coronal alignment within 3° of a neutral mechanical axis (vs 83.8% with KneeAlign, p=0.74), 81.0% had a femoral coronal alignment within 2° of perpendicular to the femoral mechanical axis (vs 89.2% with KneeAlign, p=0.31), and 92.9% had a tibial coronal alignment within 2° of perpendicular to the tibial mechanical axis (vs 81.1% with KneeAlign, p=0.12). Regarding sagittal alignment, the IM cohort had 90.5% of patients with femoral component alignment within 2° of optimum (vs 91.9% with KneeAlign, p=0.83) and 92.9% had a tibial component alignment within 2° of the optimal tibial slope (vs 89.2% with KneeAlign, p=0.57). The mean tourniquet time (from incision to completion of coronal bone resections) in the IM cohort was 16.5± 8.9 minutes vs 22.2 ± 7.6 minutes in the KneeAlign cohort (p<0.003).Conclusion:Accelerometer-based, portable navigation has a statistically similar outcome in alignment following TKA as IM guides. It is noted that using the portable navigation device does prolong surgical time compared to conventional IM surgery and this may be due to the learning curve.