Wear of the polyethylene (PE) insert in total knee replacements can lead to wear-particle and fluid-pressure induced osteolysis. One major factor affecting the wear behaviour of the PE insert in-vivo is the surface characteristics of the articulating femoral components. Contemporary femoral components available in Canada are either made of cast Cobalt Chromium (CoCr) alloy or have an oxidized zirconium surface (Oxinium). The latter type of femoral components have shown to have increased abrasive wear resistance and increased surface wettability, thus leading to reduced PE wear in-vitro compared with conventional cast CoCr components. Although surface damage has been reported on femoral components in general, there have been no reports in the literature as to what extent the recommended operating techniques affect the surface tribology of either type of femoral component.

Twenty-two retrieved total knee replacements were identified with profound surface damage on the posterior aspect of the femoral condyles. The femoral components were of three different knee systems: five retrievals from the NexGen(r) total knee system (Zimmer Inc., Warsaw, IN), twelve retrievals from the Genesis II(r) total knee system (CoCr alloy or Oxinium; Smith & Nephew Inc., Memphis, TN), and five retrievals from the Duracon(r) total knee system (Stryker Inc., Mahwah, NJ). Reasons for revision were all non-wear-related and included aseptic loosening in two cases, painful flexion instability, and chronic infection. All retrieved femoral components showed evidence of surface damage on the condyles, at an average of 99° flexion (range, 43° – 135° flexion). Titanium (Ti) alloy transfer and abrasive surface damage were evident on all retrieved CoCr alloy femoral components that came in contact with Ti alloy tibial trays. Surface damage on the retrieved Oxinium femoral components was gouging, associated with the removal and cracking of the oxide and exposure of the zirconium alloy substrate material. CoCr alloy femoral components that had unintended contact with CoCr alloy tibial trays also showed evidence of gouging and abrasive wear.

All femoral components showed severe surface damage in the posterior aspect of the condyles. The femoral surface was heavily scratched and the oxidized zirconium coating surface appeared removed. The surface analysis suggested that the surface damage most likely occurred during the time of initial implantation. In particular, it appeared that the femoral condyles were resting on the posterior aspect of the tibial tray in flexion, thus scratching the femoral components. Such scratches could potentially lead to accelerated PE insert wear and reduced implant longevity, thus making expensive revisions surgery necessary. The authors strongly suggest a revision of the current operating techniques recommended by the implant manufacturer to prevent this type of surface damage from occurring.

A primary goal of revision Total Knee Arthroplasty (rTKA) is restoration of the Joint Line (JL) and Posterior Condylar Offsets (PCO). The presence of a native contralateral joint allows JL and PCO to be inferred in a way that could account for patient-specific anatomical variations more accurately than current techniques. This study assesses bilateral distal femoral symmetry in the context of defining targets for restoration of JL and PCO in rTKA. 566 pre-operative CTs for bilateral TKAs were segmented and landmarked by two engineers. Landmarks were taken on both femurs at the medial and lateral epicondyles, distal and posterior condyles and hip and femoral centres. These landmarks were used to calculate the distal and posterior offsets on the medial and lateral sides (MDO, MPO, LDO, LPO respectively), the lateral distal femoral angle (LDFA), TEA to PCA angle (TEAtoPCA) and anatomic to mechanical axis angle (AAtoMA). Mean bilateral differences in these measures were calculated and cases were categorised according to the amount of asymmetry. The database analysed included 54.9% (311) females with a mean population age of 68.8 (±7.8) years. The mean bilateral difference for each measure was: LDFA 1.4° (±1.0), TEAtoPCA 1.3° (±0.9), AAtoMA 0.5° (±0.5), MDO 1.4mm (±1.1), MPO 1.0mm (±0.8). The categorisation of asymmetry for each measure was: LDFA had 39.9% of cases with <1° bilateral difference and 92.4% with <3° bilateral difference, TEAtoPCA had 45.8% <1° and 96.6% <3°, AAtoMA had 85.7% <1° and 99.8% <3°, MDO had 46.2% <1mm and 90.3% <3mm, MPO had 57.0% <1mm and 97.9% <3mm. This study presents evidence supporting bilateral distal femoral symmetry. Using the contralateral anatomy to obtain estimates for JL and PCO in rTKA may result in improvements in intraoperative accuracy compared to current techniques and a more patient specific solution to operative planning

Introduction. Oriental people habitually adopt formal sitting and squatting postures, the extreme flexion of the knees allowing of this. The influence exercised by pressure and posture are, therefore, found at the posterior side of knee joint. However, we don't have many report about articular cartilage of posterior femoral condyle. Objectives. The purpose of this study was to reveal the accurate prevalence and related factors to the presence of degenerative changing of the articular cartilage of posterior femoral condyle in cadaveric knee joints. Methods. One hundred and thirty two knees from 66 cadavers (42 male knees and 24 female knees, formalin fixed, Japanese anatomical specimens) were included in this study. The average age of the cadavers was 81.4 (56–101) years. Knees were macroscopically evaluated the depth of cartilage degeneration of the patellofemoral joint, medial and lateral femoral condyle, medial and lateral posterior femoral condyle following the Outerbridge's classification. Grading was as follows: Grade 1: normal cartilage or softening and swelling of the cartilage. Grade 2: partial-thickness defect which did not reach the subchondral bone and was less than 1.3 cm in diameter. Grade 3: partial-thickness defect which did not reach the subchondral bone and was more than 1.3 cm in diameter. Grade 4: exposed subchondral bone and visible reactive tissue formation. When there were multiple lesions of different Outerbridge's classification grades, the sizes of the lesions were added up. Lesions with degenerative changes more severe than Outerbridge's classification grade 3 were regarded as OA lesions. Statistical analysis was performed to reveal the correlation between the occurrences of cartilage degeneration of medial and lateral posterior femoral condyle and medial and lateral femoral condyle and gender. Results. The prevalence of OA-positive was 48.5% (64 knees). Analyzing in the prevalence in gender, male was 31% (26 knees) OA-positive, female was 79.2% (38knees) OA-positive. The frequency of OA-positive was significantly higher in females than in males (P < 0.001). The prevalence of OA-positive in posterior condyle was 53.1% (34 knees) in 64 knees of OA-positive. Analyzing in the prevalence in gender, male was 15.4% (4 knees) in 26 knees of OA-positive, female was 78.4% (30knees) in 38 knees of OA-positive. The frequency of OA-positive in posterior condyle was significantly higher in females than in males (P < 0.001). Conclusions. In this study, the prevalence of OA-positive in posterior condyle was evaluated in cadaveric knees. The prevalence of OA-positive in posterior condyle was 53.1% in OA-positive knees, and was significantly correlated with the gender

Introduction. The posterior condylar axis of the knee is the most common reference for femoral anteversion. However, the posterior condyles, nor the transepicondylar axis, provide a functional description of femoral anteversion, and their appropriateness as the ideal reference has been questioned. In a natural standing positon, the femur can be internally or externally rotated, altering the functional anteversion of the native femoral neck or prosthetic stem. Uemura et al. found that the femur internally rotates by 0.4° as femoral anteversion increases every 1°. The aim of this study was to assess the relationship between femoral anteversion and the axial rotation of the femur before and after total hip replacement (THR). Method. Fifty-nine patients had a pre-operative CT scan as part of their routine planning for THR. The patients were asked to lie in a comfortable position in the CT scanner. The internal/external rotation of the femur, described as the angle between the posterior condyles and the CT coronal plane, was measured. The native femoral neck anteversion, relative to the posterior condyles, was also determined. Identical measurements were performed at one-week post-op using the same CT methodology. The relationship between femoral IR/ER and femoral anteversion was studied pre- and post-op. Additionally, the effect of changing anteversion on the axial rotation of the femur was investigated. Results. There was a strong correlation between axial rotation of the femur and femoral anteversion, both pre-and post-operatively. Pearson correlation coefficients of 0.64 and 0.66 respectively. This supported Uemura et al.'s findings that internal rotation of the femur increases with increasing anteversion. Additionally, there was a moderate correlation, r = 0.56, between the change in axial rotation of the femur and change in anteversion. This trend suggested that external rotation of the leg would increase, if stem anteversion was decreased from the native. Conclusions. Patients with high femoral anteversion may have a natural mechanism of “correction” with femoral internal rotation. Equally, patients with femoral retroversion tend to naturally externally rotate their leg. Decreasing stem anteversion from native, trended toward an increase in external rotation of the femur. This finding is supported by the clinical observation of patients with high anteversion and compensatory in-toe, who have normal foot progression angle post-operatively after having their anteversion decreased. These findings have implications when planning implant alignment in THR

INTRODUCTION. Mechanical alignment in TKA introduces significant anatomic modifications for many individuals, which may result in unequal medial-lateral or flexion-extension bone resections. The objective of this study was to calculate bone resection thicknesses and resulting gap sizes, simulating a measured resection mechanical alignment technique for TKA. METHODS. Measured resection mechanical alignment bone resections were simulated on 1000 consecutive lower limb CT-Scans from patients undergoing TKA. Bone resections were simulated to reproduce the following measured resection mechanical alignment surgical technique. The distal femoral and proximal tibial cuts were perpendicular to the mechanical axis, setting the resection depth at 8mm from the most distal femoral condyle and from the most proximal tibial plateau (Figure 1). If the resection of the contralateral side was <0mm, the resection level was increased such that the minimum resection was 0mm. An 8mm resection thickness was based on an implant size of 10mm (bone +2mm of cartilage). Femoral rotation was aligned with either the trans-epicondylar axis or with 3 degrees of external rotation to the posterior condyles. After simulation of the bone cuts, media-lateral gap difference and flexion-extension gaps difference were calculated. The gap sizes were calculated as the sum of the femoral and tibial bone resections, with a target bone resection of 16mm (+ cartilage corresponding to the implant thickness). RESULTS. For both the varus and valgus knees, the created gaps in the medial and lateral compartments were reduced in the vast majority of cases (<16mm). The insufficient lateral condyle resection distalises the lateral joint surface by a mean of 2.1mm for the varus and 4.4mm for the valgus knees. The insufficient medial tibial plateau resection proximalises the medial joint surface by 3.3mm for the varus and 1.2mm for the valgus knees. Medio-lateral gap imbalances in the extension space of more than 2mm) occurred in 25% of varus and 54% of valgus knees and significant imbalances of more than 5mm were present in up to 8% of varus and 19% of valgus knees. Higher medio-lateral gap imbalances in the flexion space were created with trans epicondylar axis versus 3 degrees to the posterior condyles (p<0.001). Using trans epicondylar axis, only 49% of varus and 18% of valgus knees had less than 3mm of imbalance in both media-lateral and flexion-extension gaps together. DISCUSSION AND CONCLUSION. A systematic use of the tested measured resection mechanical alignment technique for TKA leads to many cases with medio-lateral or flexion-extension gap asymmetries. Some medio-lateral imbalances may not be correctable surgically and may results in TKA instability. Other versions of the mechanical alignment technique or other alignment methods that better reproduce knee anatomies should be explored. For any figures or tables, please contact the authors directly

Introduction. One of the important criteria of the success of TKR is achievement of the Flexion ROM. Various factors responsible to achieve flexion are technique, Implant and patient related. Creation of the Posterior condylar offset is one such important factor to achieve satisfactory flexion. Aim. To correlate post op femoral condylar offset to final flexion ROM at 1 yr. post op. Methods. This is a clinico-radiological study of the cases done prospectively between September 2011 and August 2012. Inclusion criteria:. All patients undergoing Bilateral TKRs and have agreed for the follow up at 1 yr. Exclusion criteria:. Patients who had previous bony surgery on lower end femur. Patients with previous fracture of lower end femur. All the patients had PS PFC Sigma (De Puy, Warsaw) components cemented. ROMs were measured at 6 weeks, 3 months, & 1 year post op. The last reading was taken as final flexion ROM as measured by a Physiotherapist with the help of a Goniometer. Results. We had 21 cases of Bilateral TKRs who satisfied our criteria. Pre and post op femoral condylar offset was measured in mm. on lateral x ray. Pre and post op flexion was measured. Results showed that variation in the posterior femoral offset by > 3mm in post op x ray was related to loss of flexion of an average 21 deg. (16 – 24 degrees). Greater the deflection from the normal offset, greater was the loss of flexion. These patients also showed lesser improvement in KSS functional score. Discussion. Flexion is one of the most important yardsticks for the measurement of success of TKR. This factor is more important more so in Asian population. Literature has shown that three important determinants for good flexion are…. Posterior Condylar Offset Restoration. Tibial slope restoration. Femoral Roll back in flexion. An increased offset permits greater flexion before impingement between the tibial insert and the femur. In our study we kept Tibial slope and Femoral Roll back constant by using the same prosthesis. The femoral condylar offset changed as per the size of the AP femoral cutting block. (Anterior referencing guide used). Overresection of the posterior condyles reduced the posterior femoral condylar offset and hence significant loss of post op flexion. The shorter posterior condyle of smaller femoral component can increase the potential for bone impingement proximal to the posterior condyles. In our study the opposite side replaced knee acted as a control. It is generally stated that after a TKR flexion can improve upto 1 year and hence was taken as final possible flexion. Conclusion. Keeping Tibial slope and Femoral roll back constant during the surgery, posterior condylar offset restoration within 3 mm of its original pre op offset was necessary to achieve satisfactory flexion at 1 year. Undersizing the femoral component to achieve more flexion is perhaps suboptimal. Appropriate AP femoral sizing is a must to restore the normal offset

Introduction. CT based systems that are used to create custom components and custom cutting guides in total knee arthroplasty (TKA) have variable methods for accounting for the thickness of remaining cartilage that may influence component sizing and bone resection. Little information has been published about the thickness of this cartilage, especially on the posterior femoral condyles. Failure to account for this cartilage may lead to under-sizing of the femoral component, or a reduction in the posterior condylar offset that may adversely affect flexion after TKA. Methods. This IRB approved, retrospective study included 140 consecutive patients who underwent primary TKA. The medial and lateral posterior condylar bone cuts were performed in the usual manner with mechanical instruments. The resected specimen was sectioned in the sagital plane and the cartilage thickness was measured at the mid portion to the nearest millimeter. Results. The mean cartilage thickness was 1.7 mm (range, 0 to 4 mm) on the medial posterior condyle and 2.0 mm (range, 0 to 5 mm) on the lateral posterior condyle. There was no correlation between the remaining medial and lateral posterior condylar cartilage thickness (p=0.35). Conclusions. The thickness of remaining cartilage on the posterior condyles of the femur at the time of TKA is between 0 and 5 mm. This variable cartilage thickness may be poorly visualized on the CT studies used for creating custom femoral components or custom femoral cutting guides. This variability is greater than the 3 to 4 mm differences in AP measurement between femoral sizes in most contemporary TKA systems. Therefore, CT based custom systems may reproduce femoral sizing and posterior condylar offset less well than off the shelf femoral components implanted with conventional instruments. Future studies will be needed to evaluate the accuracy of component sizing between CT versus MRI based systems

Introduction. Following total knee arthroplasty (TKA), some patients show patella baja. It is possible that patella baja after posterior stabilized (PS)-type TKA causes the patellar clunk syndrome and limitation of flexion. The purpose of this study was to examine patellar height before and after PS-type TKA and identify the factors related to the change in patellar height. Methods. Lateral X-ray films were taken at 90 degrees flexion before and after TKA using fluoroscopy in 87 patients (95 knees) (Fig. 1a, b). The components and surgical technique for TKA were Scorpio NRG (Stryker) and the modified gap control technique, respectively. The Insall-Salvati ratio (ISR) and the Labelle-Laurin method (LL) were measured as parameters of patellar height (Fig. 1c, d). Posterior condylar offset (PCO) (Fig. 1e), the distance from the anterior femoral line to the tibial tuberosity (TA), and the distance from the tibial tuberosity to the posterior condyle of the femur [TP; {TA-F (the length of the femoral condyle)}] (Fig. 1f) were examined as parameters that could be associated with the change in patellar height. All parameters were divided by patellar length to compensate for the expansion rate in each photograph. The mean LL/P, PCO/P, TA/P, and TP/P before TKA were set at 100%. Results. The mean ISR was not significantly different before and after TKA, but the mean LL before TKA was significantly decreased after TKA (−231%). The mean PCO/P of the femur were not significantly different after TKA. The mean length of TA/P and TP/P increased significantly after TKA (TA/P: 103%, TP/P: 110%). Sex, patellar replacement, lateral release of the patella and MCL release were not significantly related with the difference in LL after TKA. The difference in LL after TKA was significantly correlated with the distance from the tibial tuberosity to the posterior condyle of the femur (R. 2. = 0.44, Fig. 2). The difference in LL after TKA was not correlated with flexion motion after TKA. The patellar clunk syndrome after TKA was not seen in any of the cases. Discussion. The patellar height defined by the length from the anterior femoral line to the top of the patella was lower after PS-type TKA than before TKA, although the ISR did not change after TKA. The changing patellar height correlated with the difference in the distance from the tibial tubercle to the posterior condyle of the femur before and after TKA. Since the PCO was not significantly changed after TKA, it appears that the length of proximal tibia was prolonged. The prolonged proximal tibia and the distal positioning of the patella after TKA might be due to the reduced pre-operative instability of the knee and the inferior traction of the patellar tendon and quadriceps muscle. In conclusion, the patellar height after PS-type TKA decreased after surgery. The change in patellar height was due to the length of proximal tibia

Introduction:. One of the important criteria of the success of TKR is achievement of the Flexion ROM. Various factors responsible to achieve flexion are technique, Implant and patient related. Creation of the Posterior condylar offset is one of the important factors to achieve satisfactory flexion. Aim:. To correlate post op femoral condylar offset to final flexion ROM at 1 yr. post op. Methods:. This is a clinico-radiological study of the cases done prospectively between September 2011 and August 2012. Inclusion criteria:. All patients undergoing Bilateral TKRs and have agreed for the follow up at 1 yr. Exclusion criteria: . 1). Patients who had previous bony surgery on lower end femur. 2). Patients with previous fracture of lower end femur. All the patients had PS PFC Sigma (De Puy, Warsaw) components cemented. ROMs were measured at 6 weeks, 3 months, & 1 year post op. The last reading was taken as final flexion ROM as measured by an independent Physiotherapist with the help of a Goniometer. Results:. We had 21 cases of Bilateral TKRs who satisfied our criteria. Pre and post op femoral condylar offset was measured in mm. on lateral x ray. Pre and post op flexion was measured. Results showed that variation in the posterior femoral offset by > 3 mm in post op x ray was related to loss of flexion of an average 21 deg. (16–24 degrees). Greater the deflection from the normal offset, greater was the loss of flexion. These patients also showed lesser improvement in KSS functional sco. Discussion:. Flexion is one of the most important yardsticks for the measurement of success of TKR. This factor is more important more so in Asian population. Literature has shown that three important determinants for good flexion are…. . 1). Posterior Condylar Offset Restoration. 2). Tibial slope restoration. 3). Femoral Roll back in flexion. An increased offset permits greater flexion before impingement between the tibial insert and the femur. In our study we kept Tibial slope and Femoral Roll back constant by using the same prosthesis. The femoral condylar offset changed as per the size of the AP femoral cutting block. (Anterior referencing guide used). Overresection of the posterior condyles reduced the posterior femoral condylar offset and hence significant loss of post op flexion. The shorter posterior condyle of smaller-sized femoral component can increase the potential for bone impingement proximal to the posterior condyles. In our study the opposite side replaced knee acted as a control and hence eliminating patient bius. It is generally stated that after a TKR flexion can improve upto 1 year and hence that was taken as final possible flexion. Conclusion:. Keeping Tibial slope and Femoral roll back constant during the surgery, posterior condylar offset restoration within 3 mm of its original pre op offset was necessary to achieve satisfactory flexion at 1 year. Undersizing the femoral component to achieve more flexion is perhaps suboptimal. Appropriate AP femoral sizing is a must to restore the normal offset

Introduction. Although, the total knee arthroplasty (TKA) procedure is performed to make the same extension gap (EG) and flexion gap (FG) of the knee, it is not clear how the gaps can be created equally. According to earlier reports, the gaps after bone resection (bone gaps) differ from the gaps after the trial component of the femur is set (component gaps), because of the thickness of the posterior condyle of the femoral component and the tension of the posterior capsule. The surgeon can only check the component gaps after completing the bone resection and setting the trial component and it difficult to adjust the gaps even when the acquired component gaps are inadequate. To resolve this problem, we developed a “pre-cut trial component” for use in a pre-cut technique for the femoral posterior condyle (Fig. 1). This specially made trial component allows us to check the component gaps before the final bone resection of the femur. Materials and methods. The pre-cut trial component is composed of an 8-mm-thick usual distal part and a 4-mm-thick posterior part of the femoral component, and lacks an anterior part of the femoral component. With this pre-cut trail component, 152 knees were investigated. The EG was made by standard resection of distal femur and proximal tibia. The FG was made by a 4 mm pre-cut from the posterior condylar line of the femoral posterior condyle (Fig. 2). The rotation of the pre-cut line is initially decided by anatomical landmarks. Once all of the osteophytes are removed and the bone gaps are checked, the pre-cut trial component is attached to the femur and the component gaps are estimated with the patella reduction (Fig. 3). In our experiments, these gaps were the same as the component gaps after the usual trial component was set via the measured resection technique. Finally, the femur is completely resected according to the measurements of the component gaps with the pre-cut trial component. Results. The bone gaps were 18.4±2.4 (mean ± standard deviation) mm in extension and 16.5±2.7 mm in flexion. From these results, the expected component gaps were 10.8±2.7 (bone gap −8) mm in extension and 12.5±2.7 (bone gap −4) mm in flexion. After the pre-cut trial component was set, the measured component gaps were 9.4±2.8 mm in extension and 12.5±2.8 mm in flexion. The EG became 1.5±1.0 mm smaller than expected, and the change of FG was 0.2±0.5 mm. While no large decrease of EG was noted, the variation was not insubstantial (0∼5 mm). Conclusion. The difference between the bone gap and component gap is very important for an adequate EG and FG in the TKA procedure. Yet with the conventional technique, the component gap is impossible to estimate before the final bone resection. If unacceptable results are discovered after the component gaps are estimated, the gaps are difficult to correct. With the technique we present here, the component gaps can be checked before final bone resection and truly precise gap control can be attained

Mechanical alignment (MA) techniques for total knee arthroplasty (TKA) may introduce significant anatomic modifications, as it is known that few patients have neutral femoral, tibial or overall lower limb mechanical axes. A total of 1000 knee CT-Scans were analyzed from a database of patients undergoing TKA. MA tibial and femoral bone resections were simulated. Femoral rotation was aligned with either the trans-epicondylar axis (TEA) or with 3° of external rotation to the posterior condyles (PC). Medial-lateral (DML) and flexion-extension (DFE) gap differences were calculated. Extension space ML imbalances (3mm) occurred in 25% of varus and 54% of valgus knees and significant imbalances (5mm) were present in up to 8% of varus and 19% of valgus knees. For the flexion space DML, higher imbalance rates were created by the TEA technique (p < 0 .001). In valgus knees, TEA resulted in a DML in flexion of 5 mm in 42%, compared to 7% for PC. In varus knees both techniques performed better. When all the differences between DML and DFE are considered together, using TEA there were 18% of valgus knees and 49% of varus knees with < 3 mm imbalances throughout, and using PC 32% of valgus knees and 64% of varus knees. Significant anatomic modifications with related ML or FE gap imbalances are created using MA for TKA. Using MA techniques, PC creates less imbalances than TEA. Some of these imbalances may not be correctable by the surgeon and may explain post-operative TKA instability. Current imaging technology could predict preoperatively these intrinsic imitations of MA. Other alignment techniques that better reproduce knee anatomies should be explored

BACKGROUND. Conventional TKA surgery attempts to restore patients to a neutral alignment, and devices are designed with this in mind. Neutral alignment may not be natural for many patients, and may cause dissatisfaction [1]. To solve this, kinematical alignment (KA) attempts to restore the native pre-arthritic joint-line of the knee, with the goal of improving knee kinematics and therefore patient's function and satisfaction [1]. Proper prosthetic trochlea alignment is important to prevent patella complications such as instability or loosening. However, available TKA components have been designed for mechanical implantation, and concerns remain relating the orientation of the prosthetic trochlea when implants are kinematically positioned. The goal of this study is to investigate how a currently available femoral component restores the native trochlear geometry of healthy knees when virtually placed in kinematic alignment. METHODS. The healthy knee OAI (Osteoarthritis Initiative) MRI dataset was used. 36 MRI scans of healthy knees were segmented to produce models of the bone and cartilage surfaces of the distal femur. A set of commercially available femoral components was laser scanned. Custom 3D planning software aligned these components with the anatomical models: distal and posterior condyle surfaces of implants were coincident with distal and posterior condyle surfaces of the cartilage; the anterior flange of the implant sat on the anterior cortex; the largest implant that fitted with minimal overhang was used, performing ‘virtual surgery’ on healthy subjects. Software developed in-house fitted circles to the deepest points in the trochlear grooves of the implant and the cartilage. The centre of the cartilage trochlear circle was found and planes, rotated from horizontal (0%, approximately cutting through the proximal trochlea) through to vertical (100%, cutting through the distal trochlea) rotated around this, with the axis of rotation parallel to the flexion facet axis. These planes cut through the trochlea allowing comparison of cartilage and implant surfaces at 1 degree increments - (fig.1). Trochlear groove geometry was quantified with (1) groove radial distance from centre of rotation cylinder (2) medial facet radial distance (3) lateral facet radial distance and (4) sulcus angle, along the length of the trochlea. Data were normalised to the mean trochlear radius. The orientation of the groove was measured in the coronal and axial plane relative to the flexion facet axis. Inter- and intra-observer reliability was measured. RESULTS. In the coronal plane, the implant trochlear groove was oriented a mean of 8.7° more valgus (p<0.001) than the normal trochlea. The lateral facet was understuffed most at the proximal groove between 0–60% by a mean of 5.3 mm (p<0.001). The medial facet was understuffed by a mean of 4.4 mm between 0–60% (p<0.001) - (fig.2). CONCLUSIONS. Despite attempts to design femoral components with a more anatomical trochlea, there is significant understuffing of the trochlea, which could lead to reduced extensor moment of the quadriceps and contribute to patient dissatisfaction

Mechanical alignment (MA) techniques for total knee arthroplasty (TKA) introduces significant anatomic modifications and secondary ligament imbalances. A restricted kinematic alignment (rKA) protocol was proposed to minimise these issues and improve TKA clinical results. A total of 1000 knee CT-Scans were analyzed from a database of patients undergoing TKA. rKA tibial and femoral bone resections were simulated. rKA is defined by the following criteria: Independent tibial and femoral cuts within ± 5° of the bone neutral mechanical axis and, a resulting HKA within ± 3° of neutral. Medial-lateral (ΔML) and flexion-extension (ΔFE) gap differences were calculated and compared with MA results. With the MA technique, femoral rotation was aligned with either the trans-epicondylar axis (TEA) or with 3° of external rotation to the posterior condyles (PC). Extension space ML imbalances (>/=3mm) occurred in 33% of TKA with MA technique versus 8% of the knees with rKA (p /=5mm) were present in up to 11% of MA knees versus 1% rKA (p < 0 .001). Using the MA technique, for the flexion space ΔML, higher imbalance rates were created by the TEA technique (p < 0 .001). rKA again performed better than both MA techniques using TEA of 3 degrees PC techniques (p < 0 .001). When all the differences between ΔML and ΔFE are considered together: using TEA there were 40.8% of the knees with < 3 mm imbalances throughout, using PC this was 55.3% and using rKA it was 91.5% of the knees (p < 0 .001). Significantly less anatomic modifications with related ML or FE gap imbalances are created using rKA versus MA for TKA. Using rKA may help the surgeon to balance a TKA, whilst keeping the alignment within a safe range

Introduction. Two principal targets are dominating the spectrum of goals in total knee arthroplasty: first of all the orthopedic surgeon aims at achieving an optimal pain-free postoperative kinematic motion close to the individual physiologic range of the individual patient and secondly he aims for a concurrent high ligament stability within the entire range of movement in order to establish stability for all activities of daily living. This study presents a modified surgical procedure for total knee replacement which is ligament-controlled in order to put both component into the “ligamentous frame” of the patients individual kinematics. Methods. The posterior femero-condylar index (PFC-I) is defined as being the posterior condylar offset divided by the distal antero-posterior diameter on a lateral radiograph. After careful preoperative planning the positions and orientations of the osteotomies is controlled intraoperatively via ligamentous guidance. Anterior and distal femoral osteotomy are planned on antero-posterior and lateral radiographs considering intramedular and mechanical axes as well as the orientation of the posterior condyles. Osteotomies are carried out in a stepwise fashion, starting with the anterior femoral osteotomy followed by the distal femoral osteotomy as planned. Then the extension gap is finalized by tensioning the ligaments and “top-down” referencing the level of the tibial osteotomy. After rotating the femur into the 90°-flexion position the flexion gap is finalized by referencing the level of the posterior condyle osteotomy in a “bottom-up” fashion to the tibial osteotomy. Hence, this technique determines the size of the femoral component with the last osteotomy. It likewise respects the new, ACL-lacking ligamentous framework and it drives the prosthetic components to fit into the new ligamentous envelope to follow the modified kinematics. Results. More than 130 patients have been operated on using this surgical technique, 104 of them have been followed-up after a minimum of one year: age 73+/−9, m/f 37/67, 71% had a varus, 29% a valgus-deformity. In all patients a subvastus approach was applied, 12 from medial, 92 from lateral. Mean flexion reached 122°+/−7.4 and a 120°-flexion or more was achieved by 86% of the patients. All patients reveived a LCS total knee prosthesis with either a rotating or an antero-posterior gliding inlay. No fixed tibial inlays were used. Antero-posterior translation of the APG-insert was 13 to 16mm immediately postoperatively whereas after one year it decreased to 4 to 10mm. We succeeded in reconstructing the posterior femero-condylar index (PFC-I) and found a linear correlation of 0.98 +/−0.06 of pre- to postoperative PFC-I. Conclusion. This PCL-retaining surgical technique respects the new, ACL-lacking kinematics in total knee replacement. The anterior and distal femoral osteotomies are femur-axis-controlled while the extension and flexion gaps are ligament-controlled. The size of the femoral component is regarded as a variable within the procedure and is only determined while performing the last osteotomy, i.e. the posterior condylar osteotomy. This technique is suitable for both PCL-retaining and also for PCL–sacrificing techniques

Introduction. A previous computational study on an all-polymer PEEK-on-UHMWPE total knee replacement implant showed improved periprosthetic bone loading, compared to a conventional implant [1]. That study used a simulated gait cycle to determine distal loading, but a patella was not included. Substantial distal decrease of bone remodeling stimulus was found, in accordance with previous reports [2], but it was not consistent with other clinical and post-mortem DEXA results, which found the largest loss of bone stock in the anterior region [3,4]. As patellofemoral forces are relatively low during gait compared to squatting, we simulated a deep squat, expecting that a high-demand activity would provide similar indications of bone loss as literature [3,4]. Consequently, we applied both high tibiofemoral and patellofemoral loads, to provide more insight in the potential benefits of a new PEEK-Optima® femoral component on periprosthetic bone stock. Methods. We adopted a deep squat finite element model from Zelle et al. and included quasi-static deep flexion and load sharing at the posterior condyles [6]. A new implant design was inserted, with three variations in material properties: intact, CoCr and PEEK. The stiffness of the femoral elements was mapped from CT and applied to either the cut femur only (CoCr and PEEK) or the entire femoral construct (intact). The strain energy density (SED) was evaluated in the periprosthetic region as a measure for bone remodeling stimulus. To examine the effects of the entire exercise, SED values were integrated over all increments. Results. During squat the highest SED values were found at the intercondylar region, behind the posterior condyles and behind the anterior flange, extending further inward to the bone. Both the lateral and medial view of the periprosthetic region show markedly different SED patterns from the conventional CoCr implant. Higher values originating proximally extended to lower values in the anterodistal region (Figure 1). However, in the CoCr reconstruction these anterodistal patterns less prominent or even absent. In Figure 2, simulated DEXA images are presented showing the bone remodeling stimulus throughout the periprosthetic volume. Overall, the image for CoCr shows darker areas than PEEK and the reference, further corroborating the findings shown in Figure 1. Moreover, it is visible that the PEEK reconstruction had SED values similar to the reference in the femoral component region. Discussion. This study has corroborated that the influence of the patella in high-demanding tasks is of great importance to the anterior periprosthetic bone stock [4,5]. The loss of bone remodeling stimulus in the CoCr reconstruction is in accordance with literature findings [2–4]. The resemblance of PEEK to the intact reference suggests that the new PEEK-Optima® femoral component could largely retain the integrity of the periprosthetic bone

Dual plating of the medial and lateral distal femur has been proposed to reduce angular malunion and hardware failure secondary to delayed union or nonunion. This strategy improves the strength and alignment of the construct, but it may compromise the vascularity of the distal femur paradoxically impairing healing. This study investigates the effect of dual plating versus single plating on the perfusion of the distal femur. Ten matched pairs of fresh-frozen cadaveric lower extremities were assigned to either isolated lateral plating or dual plating of a single limb. The contralateral lower extremity was used as a matched control. A distal femoral locking plate was applied to the lateral side of ten legs using a standard sub-vastus approach. Five femurs had an additional 3.5mm reconstruction plate applied to the medial aspect of the distal femur using a medial sub-vastus approach. The superficial femoral artery and the profunda femoris were cannulated at the level of the femoral head. Gadolinium MRI contrast solution (3:1 gadolinium to saline ration) was injected through the arterial cannula. High resolution fat-suppressed 3D gradient echo sequences were completed both with and without gadolinium contrast. Intra-osseous contributions were quantified within a standardized region of interest (ROI) using customized IDL 6.4 software (Exelis, Boulder, CO). Perfusion of the distal femur was assessed in six different zones. The signal intensity on MRI was then quantified in the distal femur and comparison was made between the experimental plated limb and the contralateral, control limb. Following completion of the MRI protocol, the specimens were injected with latex medium and the extra-osseous vasculature was dissected. Quantitative MRI revealed that application of the lateral distal femoral locking plate reduced the perfusion of the distal femur by 21.7%. Within the dual plating group there was a reduction in perfusion by 24%. There was no significant difference in the perfusion between the isolated lateral plate and the dual plating groups. There were no regional differences in perfusion between the epiphyseal, metaphyseal or meta-diaphyseal regions. Specimen dissection in both plating groups revealed complete destruction of any periosteal vessels that ran underneath either the medial or lateral plates. Multiple small vessels enter the posterior condyles off both superior medial and lateral geniculate arteries and were preserved in all specimens. Furthermore, there was retrograde flow to the distal most aspect of the condyles medially and laterally via the inferior geniculate arteries. The medial vascular pedicle was proximal to the medial plate in all the dual plated specimens and was not disrupted by the medial sub-vastus approach in any specimens. Fixation of the distal femur via a lateral sub-vastus approach and application of a lateral locking plate results in a 21% reduction in perfusion to the distal femur. The addition of a medial 3.5mm reconstruction plate does not significantly compromise the vascularity of the distal femur. The majority of the vascular insult secondary to open reduction, internal fixation of the distal femur occurs with application of the lateral locking plate

Introduction. Appropriate femoral stem anteversion is an important factor in maintaining stability and maximizing the performance of the bearing after total hip replacement (THR). The anteversion of the native femoral neck has been shown to have a significant effect on the final anteversion of the stem, particularly with a uncemented femoral component. The aim of this study was to quantify the variation in native femoral neck anteversion in a population of patients requiring total hip replacement. Methods. Pre-operatively, 1215 patients received CT scans as part of their routine planning for THR. Within the 3D planning, each patient's native femoral neck anteversion, measured in relation to the posterior condyles of the knee, was determined. Patients were separated into eight groups based upon gender and age. Males and females were divided by those under 55 years of age, those aged 55 to 64, 65 to 74 and those 75 or older. Results. The median anteversion in males was 12.7° (−27.1°–45.5°, IQR 6.0°–19.1°), compared to female anteversion of 16.0° (− 14.0°–54.5°, IQR 9.7°– 22.4°). These gender differences were statistically significant, p < 0.0001. Femoral anteversion in young males (<55) was significantly higher than in older males (>75), p=0.002. This age-related difference approached significance in females, p = 0.06. 14% of patients had extreme anteversion (<0° or >30°). Conclusions. The Native femoral neck anteversion in patients requiring THR is widely variable, with a range of over 80°. Females have more anteverted femurs than males. Femoral anteversion in young males was significantly higher than in older males. This age-related difference approached significance in females. Having an understanding of 3D patient morphology can greatly assist in pre-operative planning of THR, as post-op stem anteversion is likely influenced by the anteversion of the native femoral neck

Introduction:. Total knee arthroplasty (TKA) should aim to adjust the component gap (CG) difference between extension and flexion. However, this difference cannot be measured without placement of a femoral component. The bone gap reportedly decreases in extension after component setting. In contrast, it may be possible to use the mean value of the CG difference in several patients to adjust femoral resection amount beforehand. The purpose of this study is to evaluate the technique of adjusting CG difference using the mean values with measured resection technique (MRT) in TKA. Materials and methods:. The subjects were 222 knees (40 male knees, 182 female knees; mean age 70.4 years). To adjust the CG difference after estimation, the femoral posterior condylar pre-cut technique was used. Extension gap was created by usual bone resection; 4 mm of the femoral posterior condyle was pre-cut, and after all osteophytes and soft tissues had been treated, a pre-cut trial component (thickness of 8 mm for distal femur and 4 mm for posterior condyle without the anterior portion) was mounted, achieving the same condition as the setting of a femoral component in MRT (Fig. 1). When the posterior cruciate ligament (PCL) could be easily preserved by intraoperative gap assessments, the PCL was preserved (190 knees, 86%). Results:. The CG measured intraoperatively were 9.4 ± 2.8 mm (mean ± S.D.) in extension and 12.2 ± 2.8 mm in flexion, and the difference (flexion - extension) was 2.8 ± 2.6 mm. The mean difference was not large but the variation was large (−3 ∼ 11 mm). When the acceptable range of CG difference (flexion - extension) is set at 0 to 3 mm, only 57% of the patients were included within this range; when 2 mm of the distal femur was cut beforehand in all patients considering the mean CG difference of 2.8 mm, 53% of the patients were within the acceptable range and 42% had 3 mm resection (Fig. 2). When the acceptable range was expanded to −2 mm to 3 mm, 64% of the patients were in this range, whereas this figure was 76% with an additional 2 mm resection of the distal femur and 72% with 3 mm resection. Even after expanding the acceptable range for CG difference to 5 mm and adjusting the distal femoral cut, one fourth of the patients were outside of the acceptable range (Fig. 3). Discussion:. This study showed that the CG using MRT was larger in flexion by a mean of 2.8 mm; however, the variation was too large to manage by larger femoral distal cut according to the mean difference beforehand. Although the PCL was preserved in 190 knees, it is anticipated that gaps in flexion will enlarge when PCL resection is selected for all patients, which may further increase the gap requiring adjustment. To resolve such issues, we use the femoral pre-cut technique and pre-cut trial components. With this method, we can control the CG as we want by adjustment of final femoral bone resection in each patient

Introduction. Achieving a well-balanced midflexion and flexion soft tissue envelope is a major goal in Total Knee Arthroplasty (TKA). The definition of soft tissue balance that results in optimal outcomes, however, is not well understood. Studies have investigated the native soft tissue envelope in cadaveric specimen and have shown loosening of the knee in flexion, particularly on the lateral side. These methods however do not reflect the post TKA environment, are invasive, and not appropriate for intra-operative use. This study utilizes a digital gap measuring tool to investigate the impact of soft tissue balance in midflexion and flexion on post-operative pain. Methods. A prospective multicenter multi-surgeon study was performed in which patients underwent TKA with a dynamic ligament-balancing tool in combination with a robotic-assisted navigation platform. All surgeries were performed with APEX implants (Corin Ltd., USA) using a variety of tibia and femur first techniques. Gap measurements were acquired under load (average 80 N) throughout the range of motion during trialing with the balancing tool inserted in place of the tibial trial. Patients completed KOOS pain questionnaires at 3months±2weeks post-op. Linear correlations were investigated between KOOS pain and coronal gap measurements in midflexion (30°–60°) and flexion (>70°). T-tests were used to compare outcomes between categorical data. Results. 92 patients underwent TKA and completed questionnaires, with an average age of 68±9 years, 51% left and 57% female. No significant correlations were found between the medial and lateral gap size in midflexion or flexion and post-operative pain. Significant correlations were found between the absolute difference in the medial and lateral gaps in midflexion (r=−0.3, p=0.005) and flexion (r=−0.27, p=0.01) indicating knees with a more balance soft tissue profile reported improved pain outcomes at 3-months. Knees with less than 1mm difference in ML gap reported improved pain scores compared to those with greater gap differences in flexion (Δ=6.6, p=0.03). A significant correlation was found between the difference in average gaps in midflexion and flexion, and post-op pain (r=0.22, p=0.04) in which knees that were looser in flexion than midflexion reported improved pain outcomes. When dichotomizing these results in to looser or tighter in flexion compared to midflexion, knees that were looser reported significantly improved pain outcomes (Δ=8.2, p=0.02). Discussion and Conclusion. Improved outcomes correlated with a symmetrically balanced coronal midflexion gap and looser flexion space is consistent with the soft tissue balance of the native knee. The lack of a correlation between lateral loosening in flexion and improved outcomes may be a result of greater congruency between the femoral component and tibial insert than the native knee, preventing medial pivot lateral posterior condyle rollback motion. These results indicate that targeting the native soft tissue profile may not result in optimal outcomes when performing a TKA with a neutral tibial resection and an externally rotated femoral component. Further investigation is required to determine if these results hold with a larger data set and the effect on functional outcomes at both 3-months and longer follow-up periods. For any figures or tables, please contact authors directly

Background. Total knee arthroplasty (TKA) was primarily considered a successful procedure, several new knee implants were introduced in recent years that seek to obtain improved stability and higher flexion. One of the implant, Vanguard XP. TM. BiCruciate retaining (BCR), Zinmmer-Biomet, USA recreates a specific kinematic model through the principle of normal joint. Patients and Method. An unselected consecutive series of sixty-two patients undergoing primary TKA using the cemented total knee system between August 2016 and April 2018 were studied. Twenty-seven knees was operated using Vanguard XP, subsequently thirty-five knees were received a TKA using cruciate retaining cemented total knee system FINE. TM. CR, Nakashimamedical, Japan. Postoperatively standing AP hip-to-ankle radiographs were obtained, from which the lower extremity mechanical axis, component angle were measured. The alignment goals were a neutral mechanical axis defined as a hip-to-ankle angle of 0°with the femoral and tibial components aligned perpendicular to the mechanical axis. The total operating time were quantified utilising an operating room database. The total operating time between TKAs performed with Vanguard XP BCR and those performed with FINE CR was compared in each group. All patients postoperatively was evaluated of clinical results the Japan Orthopedics Association(JOA) Knee scores. We evaluated femoral component posterior offset (PFCO) in both of two group. The maximal protrusion of the posterior condyle, posteriorly to the extension line parallel to the tibial shaft from the edge of the posterior tibial component was measured on true lateral radiographs. Results. The JOA Knee score of Vanguard XP BCR group was 86.5±4.7 points, and the score of FINE group was 82.7±5.9 points, there was no statistical significance between the two groups on the clinical score. The operative time in Vanguard XP BCR was 137.2±14.6 minutes and significantly more compared to the time of FINE group 111.3±11.9 minutes. The mechanical axis angle in Vanguard XP BCR group was −1.3°±2.7, while FINE CR group was −0.7°±3.2, there was no statistical significance. The number of outliers for mechanical axis angle was Vanguard XP BCR group 25%, the FINE group 24%, between the two groups there was no statistical significance. The mean value of the femoral component posterior offset ratio of Vanguard XP BCR was 14.4%±0.1. The mean value of the posterior offset ratio of FINE group was 16.7%±0.1, between the two groups there was statistical significance. Discussion. Bellemans et al. first defined the concept of posterior condylar offset. They demonstrated that the maximum active flexion possible was limited by direct impingement of the posterior aspect of the tibial component against the posterior aspect of the femur. However, the offset also reduces the extension gap. An enlarged posterior femoral component may reduce the extension gap due to posterior tissue tightness. In this study, the femoral component posterior offset ratio of Vanguard XP BCR was good results compared to the CR type FINE. Clinical results and the mechanical axis angle was good both of the group, but the operative time in Vanguard XP BCR was significantly more compared to the time of FINE group. Conclusion. Good early clinical results were obtained with Vanguard XP BCR knee implant, long-term follow-up studies are needed to confirm our findings