Kinematic comparison between the knee after bicruciate stabilized total knee arthroplasty and the native knee: A cadaveric study.

BACKGROUND: Although bicruciate stabilized total knee arthroplasty (BCS-TKA) is expected to provide kinematics similar to those of the normal knee, there are limited data available for comparison of the kinematics of the knee after BCS-TKA with those of the normal knee. The purpose of this study was to confirm whether the knee after BCS-TKA are the same as those of the native knee. METHODS: Seven fresh-frozen cadavers underwent TKA using a BCS-type prosthesis with navigation system. Anteroposterior translation of the femur and internal rotation of the tibia were evaluated using the navigation system. RESULTS: There was no statistically significant difference in anteroposterior translation of the femur between the native knee and the knee after BCS-TKA in the early flexion phase (0°-30°) or in the deep flexion phase (over 100°). In the middle flexion phase (40°-90°), the knee after BCS-TKA was placed significantly more anteriorly than the native knee. The knee after BCS-TKA also showed a gradual internal rotation pattern similar to that of the native knee but the total tibial internal rotation angle was significantly smaller than that of the native knee. At each angle from 0° to 120° of flexion, internal rotation of the knee after BCS-TKA was significantly greater than that of the native knee. CONCLUSION: Kinematics of BCS-TKA is close to that of the native knee. However, there is a statistically significant difference in AP position of the femur during mid flexion and initial rotational position of the tibia between the BCS-TKA knee and the native knee.

Clinical and radiological outcomes of total hip arthroplasty using a highly porous titanium cup or a conventional hydroxyapatite-coated titanium cup: A retrospective study in Japanese patients.

BACKGROUND: A highly porous titanium cup has a unique structure that mimics human trabecular bone and is expected to achieve better outcomes due to rigid fixation and extensive bone ingrowth. Several manufacturers have developed a highly porous titanium cup; however, some have shown a high incidence of radiolucent lines (RLLs) on early postoperative radiographs. In this study, we compared the clinical and radiological outcomes of total hip arthroplasty (THA) using a highly porous titanium cup (OsseoTi, Zimmer Biomet) with those after THA using a conventional hydroxyapatite-coated titanium cup (Trident HA, Stryker). METHODS: A total of 201 hips that underwent THA using an OsseoTi cup (n = 101) or Trident cup (n = 100) were enrolled in the study. Patient characteristics, cup alignment, clinical outcome (determined by the Japanese Orthopedic Association [JOA] score), and incidence of RLLs around the cup were evaluated at 3, 6, 12, and 24 months postoperatively. RESULTS: The clinical outcome was excellent in both groups. The incidence of RLLs was 12.9% at 3 months, 20.8% at 6 months, 23.8% at 12 months, and 22.8% at 24 months after surgery in the OsseoTi group; there were no cases of RLL at any time after surgery in the Trident group. The RLLs were mainly distributed in zone 2. Despite the high rate of RLL in the OsseoTi group, the RLL were narrow and only 5% had a width of >1 mm at 24 months postoperatively. There were no cases with RLLs in all three zones. CONCLUSIONS: Despite excellent clinical outcomes in both study groups, the incidence of RLLs was higher in the OsseoTi group than in the Trident group. Although none of our cases with RLL have required revision surgery for aseptic loosening so far, these patients require careful follow-up.

Insufficient lateral joint laxity after bicruciate-retaining total knee arthroplasty potentially influences kinematics during flexion: A biomechanical cadaveric study.

BACKGROUND: Soft tissue balancing in bicruciate-retaining (BCR) total knee arthroplasty (TKA) is a challenge that must be overcome to achieve excellent clinical outcomes. However, the optimal degree of joint laxity has yet to be clarified. This cadaveric study sought to examine joint laxity after BCR TKA using a navigation system. METHODS: Knee joint laxity was quantified using an image-free navigation system in 8 intact fresh frozen cadavers under three conditions: the native knee, BCR TKA knee, and BCR TKA knee after anterior cruciate ligament resection. Rotational kinematics in the BCR TKA knee during flexion were compared according to whether joint laxity was increased or decreased. RESULTS: Knee joint laxity after BCR TKA under varus-valgus movement, anterior translation, and internal-external rotation loadings was similar to that of the native knee. However, lateral joint laxity was decreased during flexion in some cases. BCR TKA-treated knees with decreased lateral joint laxity at 90° of flexion demonstrated more limited tibial internal rotation in deep flexion than the native knee (p < 0.05). The loss of internal rotation in deep flexion was partly recovered by using a lateral insert with a posterior slope of +3°. CONCLUSIONS: Restoring optimal joint laxity was not always straightforward in BCR TKA if the 4 ligaments were preserved. Lateral joint laxity was potentially decreased in BCR TKA and may result in kinematic conflict during flexion. Surgeons should be aware of the need to achieve sufficient lateral joint laxity in this type of BCR TKA.

Postoperative radiographic evaluation and simulation study for optimal cup placement in high-hip centre total hip arthroplasty.

BACKGROUND: Achieving favourable outcomes in high-hip centre reconstruction in hip dysplasia requires the optimal cup height and size, which can provide sufficient bone coverage for stable cup fixation that fits the anteroposterior acetabular rim without increasing the cup height more than necessary. METHODS: We retrospectively reviewed 214 patients who underwent primary total hip arthroplasty (THA) and identified 30 hips with Crowe II (n = 15) or III (n = 15) developmental dysplasia of the hip (DDH). We measured the cup-centre-edge angle (cup-CE) and the vertical and horizontal distances from the teardrop. In a simulation study, we examined the cup-CE and optimal cup size by changing the cup height in 5-mm increments over a distance of 15-40 mm above the inter-teardrop line using a 3-dimensional template system. RESULTS: Postoperative radiographic evaluation revealed a mean cup-CE of 19.9° in Crowe II hips and 15.2° in Crowe III hips; the respective mean vertical distances were 26.6 mm and 27.6 mm (p = 0.511). There was no evidence of cup loosening or lateralisation at a minimum of 7 years (7-11 years) follow-up. Simulation showed that the hip centre needed to be elevated to 20 mm to acquire a cup-CE of more than 0°. More than 10° of cup-CE could be expected by elevating the hip centre to 25 mm in both Crowe II and III. CONCLUSIONS: Even in severe DDH, a high-hip centre positioned approximately 25 mm superior to the inter-teardrop line was sufficient to achieve optimal bone coverage, which could lead to more secure cup fixation.

Proximal Femoral Rotational Osteotomy for Symptomatic Femoral Retroversion†:†A Case Report.

The Rotational osteotomy for femoral retroversion has been extremely rare despite the known association between femoral neck retroversion, hip pain, and osteoarthritis. Here, we describe a case of femoral neck retroversion for which proximal femoral rotation osteotomy. A 16-year-old boy with a past history of developmental dysplasia of the both hip treated conservatively presented with a complaint of pain in left hips. On physical examination, flexion of the left hip was limited to 90° with terminal pain. Internal rotation was also limited to 10°. Computed tomography (CT) showed -7.1° anteversion of the left femur. We performed rotational osteotomy to increase femoral anteversion because conservative treatment was not effective. The postoperative course was uneventful. At 12 postoperative months, his left hip pain was completely disappeared and femoral anteversion was 34° on CT scans. Retroversion of the femur is a distinct dynamic factor that should be considered in the evaluation of mechanical causes of hip pain. Restoring the normal rotational alignment of the hip resulted in cure of the impingement due to femoral retroversion. J. Med. Invest. 67 : 214-216, February, 2020.

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.

Postoperative nausea and vomiting following lower limb surgery†:a comparison between single-injection intraarticular anesthesia and continuous epidural anesthesia.

Study Objective : the incidence of postoperative nausea and vomiting (PONV) following single-injection intraarticular anesthesia was compared to that following continuous epidural anesthesia. Design : Prospective, double-blind, randomized study. Setting : University-affiliated teaching hospital. Patients : Forty-eight patients finally participated in this study, and each group contained twenty-four patients. Interventions : Patients scheduled to undergo lower limb surgery under general anesthesia were randomly allocated into two groups, to receive either single-injection intraarticular or continuous epidural anesthesia for postoperative analgesia. Measurements : The incidence and severity of PONV, complete response rates (i.e., no vomiting or rescue antiemetic use), and pain scores were recorded 2, 24, and 48 h postoperatively. Main results : No significant differences between groups were observed in the incidence and severity of PONV, rescue antiemetic use, or complete response rate at any of the time points, but only the use of rescue analgesics was significantly less in continuous epidural anesthesia group during the 2-24h postoperative period (P=0.04). Conclusion : While the use of single-injection intraarticular anesthesia following lower limb surgery did not prevent PONV more than continuous epidural anesthesia in this study, the intraarticular technique still provides greater simplicity, safety, and cost-effectiveness. J. Med. Invest. 66 : 303-307, August, 2019.

Intraoperative analysis of the kinematics of the native knee including two-dimensional translation of the femur using a navigation system†:†a cadaveric study.

The aim of this cadaveric study was to evaluate the intraoperative kinematics of the native knee including two-dimensional translation of the femur using a navigation system. Eight native knees of 4 fresh-frozen whole-body cadavers were used for the study. The kinematics of each knee were analyzed intraoperatively using the navigation system. Although anterior-posterior translation could not be assessed directly, it could be calculated using a formula derived from the parameters in the navigation system. The native knee showed external rotation of the femur in early knee flexion, transient internal rotation in mid flexion, and gradual external rotation in late flexion. There was no marked change in the coronal rotation angle of the mechanical axis during knee flexion. The femoral center moved anteriorly in early knee flexion and posteriorly in late flexion. The distance moved in the medial-lateral direction was relatively smaller than that in the anterior-posterior direction. Two-dimensional translation of the surgical epicondylar axis showed a medial pivot-like motion. In this cadaveric study, the kinematics of the native knee, including two-dimensional translation of the femur, could be satisfactorily assessed intraoperatively using a navigation system. The intraoperative kinematics of the knee can be analyzed in more detail using this methodology. J. Med. Invest. 66 : 367-371, August, 2019.

Rotational and varus-valgus laxity affects kinematics of the normal knee: A cadaveric study.

PURPOSE: The aim of this study was to evaluate the relationship between soft tissue laxity and kinematics of the normal knee using a navigation system. METHODS: Fifteen cadaveric knees from 11 fresh frozen whole-body specimens were included in this study. The navigation system automatically recorded the rotation angle of the tibia as the internal-external (IE) kinematics and the coronal alignment of the lower limb as the varus-valgus (VV) kinematics. These measurements were made with the joint in maximal extension, at 10° intervals from 0° to 120° of flexion, and at maximal flexion during passive knee motion. For evaluation of laxity, the examiner gently applied maximum manual IE and VV stress to the knee at 0°, 30°, 60°, and 90° of flexion. RESULTS: The measurements showed almost perfect reliability. The mean correlation coefficient between the intraoperative tibial rotation angle and the intermediate angle of IE laxity was 0.82, while that between the coronal alignment of the lower limb and the intermediate angle of the VV laxity was 0.96. There was a statistically significant correlation between kinematics and laxity at all degrees of knee flexion. CONCLUSION: The present study revealed that the rotation angle of the tibia was correlated to the intermediate angle of IE laxity at 0°, 30°, 60°, and 90° of knee flexion and the coronal alignment of the lower limb also correlated to the intermediate angle of VV laxity. These findings provide important reference data on soft tissue laxity and kinematics of the normal knee.

The medial constrained insert restores native knee rotational kinematics after bicruciate-retaining total knee arthroplasty.

PURPOSE: The aim of this study was to test the hypothesis that the medial constrained insert would reproduce the native knee kinematics after bicruciate-retaining (BCR) total knee arthroplasty (TKA). METHODS: Using an image-free navigation system in six fresh-frozen whole-body cadavers, the rotation angle of the tibia at minimum flexion, at 10° intervals from 0° to 130° flexion, and at maximum flexion during manual passive knee flexion was assessed. The data was collected in native knees, in BCR TKA using a normal flat insert (BCR-XP), and in BCR TKA using a more constrained insert in the medial side (BCR-AS). The differences in the rotation angle of the tibia were statistically evaluated. RESULTS: The rotation angles of the tibia in BCR-XP were significantly different from those of the native knees both in the early flexion phase (p = 0.002 at minimum knee flexion, p = 0.002 at 0°, p = 0.041 at 10°, p = 0.009 at 20°, p = 0.026 at 30°) and in the late flexion phase (p = 0.015 at 130°, p = 0.015 at maximum knee flexion), whereas the rotational angles of the tibia in BCR-AS were similar to those of the native knee. CONCLUSION: This study shows that the rotational kinematics of the native knee is reproduced after BCR TKA with the medial constrained insert. Surgeons and implant designers should be aware that constraint of the medial side in BCR TKA is a crucial factor for restoration of native kinematics which may lead to better clinical outcome.

Acetabular Reconstruction Using a Trabecular Metal Cup with a Novel Pelvic Osteotomy Technique for Severe Acetabular Bone Defect.

CASE: A 79-year-old woman with an extreme bone defect after failed cementless total hip arthroplasty underwent revision arthroplasty with a novel technique that involved cutting the anterior iliac bone and sliding it distally to reconstruct the anterior acetabular wall. A three-dimensional printed bone model enabled understanding the details of the bone defect. The clinical outcome at 3 years after surgery was favorable. CONCLUSION: The advantages of this technique are twofold, namely, stable fixation of the cup sandwiched between the anterior and posterior walls and reconstruction of the anterior wall using living bone, which allows bone ingrowth into the cup.

Platelet-rich plasma does not reduce skeletal muscle fibrosis after distraction osteogenesis.

BACKGROUND: Skeletal muscle fibrosis caused by an increase in collagen deposition often occurs after distraction osteogenesis. Although studies are available reporting the effects of platelet-rich plasma (PRP) on tissue healing following injury, current findings remain controversial. This study focused on determining whether PRP reduces skeletal muscle fibrosis caused by distraction osteogenesis. METHODS: Tibial osteotomies were performed on 8-week-old wild type mice, and tibiae were distracted at a rate of 0.42 mm/day for 2 weeks, starting 1 week after osteotomy. Immediately after distraction was completed (3 weeks after osteotomy), PRP or phosphate buffered saline (as a sham) was injected into the gastrocnemius (GC) muscle. The GC muscles were harvested and analyzed. RESULTS: The amount and area of collagenous tissue increased in both the PRP and control groups following distraction osteogenesis, but the changes were not significantly different between both groups at all time points (p = 0.89, 0.45, 0.33 and 0.52 at 4, 6, 8 and 10 weeks). CONCLUSION: From this study, our results suggest that PRP did not significantly reduce skeletal muscle fibrosis due to distraction osteogenesis.

Native rotational knee kinematics is restored after lateral UKA but not after medial UKA.

PURPOSE: The aim of this study was to compare the intraoperative kinematics of medial and lateral unicompartmental knee arthroplasty (UKA) with those of the native knee using a navigation system. METHODS: Six fresh-frozen cadaveric knees were included in the study. Medial UKA was performed in all right knees and lateral UKA was performed in all left knees. All UKA procedures were performed with a computerised navigation system. The tibial internal rotation angle and coronal alignment of the mechanical axis during passive knee flexion were assessed as rotational and varus/valgus kinematics before and after surgery using the navigation system. RESULTS: The rotation angles of the tibia in the early flexion phase of medial UKA were significantly larger than those of native knees (p = 0.008 at minimum knee flexion, p = 0.008 at 0° knee flexion). The rotational kinematics of lateral UKA was similar to those of the native knees throughout knee flexion. There were no significant differences in varus/valgus kinematics between native and UKA knees. CONCLUSION: The rotational kinematics of the native knee was not restored after medial UKA but was preserved after lateral UKA. There were no significant differences in the varus/valgus kinematics after either medial or lateral UKA when compared with those of the native knees. Thus, the geometry of the medial tibial articular surface is a determinant of the ability to restore the rotational kinematics of the native knee. Surgeons and implant designers should be aware that the anatomical medial articular geometry is an important factor in restoration of the native knee kinematics after knee arthroplasty.

Native rotational knee kinematics are lost in bicruciate-retaining total knee arthroplasty when the tibial component is replaced.

PURPOSE: To compare the kinematics between native knees and knees that have undergone bicruciate-retaining (BCR) total knee arthroplasty (TKA) with cruciate-retaining (CR) TKA converted from BCR TKA in the same whole-body cadaveric specimen using a navigation system and, if differences exist, to investigate the point at which normal kinematics are lost during the procedure. METHODS: The rotational kinematics throughout passive flexion of the native knee and of knees after meniscectomy, femoral replacement, BCR TKA, or CR TKA were assessed in nine fresh frozen cadavers using an image-free navigation system. RESULTS: The rotational kinematic pattern of a knee after BCR TKA was different from that of a native knee, especially in the early flexion phase, and was similar to that after CR TKA. Screw-home movement was not observed after BCR TKA, but still occurred after meniscectomy or femoral replacement with intact cruciate ligaments and an intact tibial articular surface. CONCLUSION: The rotational kinematics of the native knee are not always preserved after BCR TKA. Native rotational kinematics are preserved after meniscectomy and femoral replacement, but are lost after tibial replacement in BCR TKA. Surgeons should pay close attention to maintain the anteroposterior stabilizing function of the ACL in BCR TKA, rather than to restore the native rotational kinematics.

Compression of the Femoral Vessels by a Pseudotumor after Metal-on-Metal Total Hip Arthroplasty.

Here we present a case of pseudotumor following total hip arthroplasty (THA) that resulted in a circulatory disturbance caused by compression of the femoral vasculature. A 63-year-old man presented with pain, swelling, and redness of the left leg 5 years after primary metal-on-metal THA using the AML-Plus stem, Pinnacle® acetabular cup, and 36 mm diameter Ultamet™ metal head system (DePuy Orthopaedics, Warsaw, IN). Enhanced computed tomography and magnetic resonance imaging revealed a large cystic lesion extending from the left hip anteriorly to the intrapelvic region and compressing the left femoral vessels. Percutaneous puncture of the lesion yielded a dark red aspirate and the patient was diagnosed to have a pseudotumor causing compression of the femoral vessels. We performed revision surgery to replace the metal head and metal liner with a smaller ceramic head and polyethylene liner without removal of the stem. Corrosion of the head-neck junction was identified intraoperatively with no obvious wear on the bearing surfaces. The left leg swelling and redness improved immediately postoperatively. A large pseudotumor should be kept in mind as a cause of vascular compression with unilateral leg edema in a patient who has undergone metal-on-metal THA.

Efficacy of a computed tomography-based navigation system for placement of the acetabular component in total hip arthroplasty for developmental dysplasia of the hip.

PURPOSE: Developmental dysplasia of the hip (DDH) presents a considerable surgical challenge in total hip arthroplasty (THA). Although the usefulness of computed tomography (CT)-based navigation in cup alignment has been reported, few reports have evaluated three-dimensional (3-D) cup positioning against the acetabulum specifically in patients with DDH. The purpose of this study was to evaluate the efficacy of a CT-based navigation system for alignment and spatial positioning of the cup in THA for patients with DDH. METHODS: We reviewed 174 DDH THA cases in which CT-based navigation was used, and 75 cases in which a mechanical guide was used as a control group. Postoperative cup alignment and spatial positioning were evaluated by superimposition of a 3-D cup template onto the actual implanted cup using postoperative CT images, with pelvic coordinates matching the preoperative planning. RESULTS: The proportion within the combined target zone (inclination and anteversion) was 97.7% in the navigation group and 61.3% in the non-navigation group. The mean absolute error between the intraoperative record and the postoperative measurement was 1.5° ± 1.3° for inclination and 2.1° ± 1.8° for anteversion in the navigation group. For acetabular cup positioning, the mean discrepancy between the preoperative planning and the postoperative measurements was 1.9 ± 1.6 mm on the transverse axis, 2.8 ± 2.3 mm on the longitudinal axis, and 1.7 ± 1.3 mm on the sagittal axis. CONCLUSION: THA using a CT-based navigation system achieved quite high accuracy of cup alignment angles and spatial cup positioning in primary THA for patients with DDH.

Pseudoaneurysm of the Anterior Tibial Artery following Ankle Arthroscopy in a Soccer Player.

Ankle arthroscopy carries a lower risk of vascular complications when standard anterolateral and anteromedial portals are used. However, the thickness of the fat pad at the anterior ankle affords little protection for the thin-walled anterior tibial artery, rendering it susceptible to indirect damage during procedures performed on the anterior ankle joint. To our knowledge, only 11 cases of pseudoaneurysm involving the anterior tibial artery after ankle arthroscopy have been described in the literature. Here we reported a rare case of a 19-year-old soccer player who presented with pseudoaneurysm of the anterior tibial artery following ankle arthroscopy using an ankle distraction method and underwent anastomosis for the anterior tibial artery injury. Excessive distraction of the ankle puts the neurovascular structures at greater risk for iatrogenic injury of the anterior tibial artery during ankle arthroscopy. Surgeons should look carefully for postoperative ankle swelling and pain after ankle arthroscopy.

Piriformis muscle syndrome with assessment of sciatic nerve using diffusion tensor imaging and tractography: a case report.

Piriformis muscle syndrome (PMS) is difficult to diagnose by objective evaluation of sciatic nerve injury. Here we report a case of PMS diagnosed by diffusion tensor imaging (DTI) and tractography of the sciatic nerve, which can assess and visualize the extent of nerve injury. The patient was a 53-year-old man with a 2-year history of continuous pain and numbness in the left leg. His symptoms worsened when sitting. Physical examination, including sensorimotor neurologic tests, the deep tendon reflex test, and the straight leg raise test, revealed no specific findings. The hip flexion adduction and internal rotation test and resisted contraction maneuvers for the piriformis muscle were positive. There were no abnormal findings on magnetic resonance imaging (MRI) of the lumbar spine. The transverse diameter of piriformis muscle was slightly thicker in affected side on MRI of the pelvis. A single DTI sequence was performed during MRI of the pelvis. Fractional anisotropy (FA) and the apparent diffusion coefficient (ADC) of the sciatic nerve were quantified at three levels using the fiber-tracking method. FA values were significantly lower and ADC values were significantly higher distal to the piriformis muscle. We performed endoscopic-assisted resection of the piriformis tendon. Intraoperatively, the motor-evoked potentials in the left gastrocnemius were improved by resection of the piriformis tendon. The patient's symptoms improved immediately after surgery. There was no significant difference in FA or ADC at any level between the affected side and the unaffected side 3 months postoperatively. MRI-DTI may aid the diagnosis of PMS.

Custom-Made Alumina Ceramic Total Talar Prosthesis for Idiopathic Aseptic Necrosis of the Talus: Report of Two Cases.

Two women aged 65 years and 78 years presented to our center with idiopathic necrosis of the talus. In both cases, imaging examinations showed collapse and sclerotic changes of the talar body caused by the necrosis. Both women underwent resection and placement of a third-generation custom-made alumina ceramic total talar prosthesis. Immobilization of the ankle in a short-leg cast for 3 weeks was followed by early rehabilitation. One year and 6 months after surgery, both women were able to walk without pain. Their Japanese Society for Surgery of the Foot ankle-hindfoot scale scores improved from 22 and 29/100 points to 90 and 95/100 points, respectively. To the best of our knowledge, the successful treatments of these two rare cases of idiopathic necrosis of the talus are among only a few reported cases of using a third-generation alumina ceramic prosthesis.

The Posterior Condylar Cartilage Affects Rotational Alignment of the Femoral Component in Varus Knee Osteoarthritis.

Rotational alignment of the femoral component in total knee arthroplasty (TKA) is important for patellar tracking and ligament balance. Preoperative planning based on radiography might have a potential risk for over-rotation because these X-ray based measurements can not detect asymmetric cartilage wear on posterior condyle. The purpose of this study is to evaluate the effect of the posterior condylar cartilage of varus osteoarthritic knee on rotational alignment of the femoral component in TKA. We established two different condylar twist angles (CTA) from intraoperative multiplanar reconstruction (MPR) images and intraoperative information of navigation system. The CTA measured by a navigation system that includes the cartilage (4.8±2.0°) was smaller than those measured by MPR images, which does not include the cartilage (6.6±2.1°) (p<0.05). The difference between these two angles that corresponds to the remaining posterior condylar cartilage was 1.7±1.2°. This result demonstrated that the posterior condylar cartilage might lead to over-rotational of the femoral component in varus osteoarthritic knee. Therefore, when determining rotational alignment of the femoral component, surgeons should consider the effect of the remaining posterior condylar cartilage to avoid the over-rotation of the femoral component, especially in severe varus knees. J. Med. Invest. 64: 24-29, February, 2016.