Surgical system

Abstract

A system and method for determining component positioning, orientation or configuration for a knee arthroplasty system which includes a processor configured to generate a surgical plan, such as an indicated position, orientation or configuration for a component of the knee arthroplasty system. The processor is further configured to receive data including one or more pre-operative images of a subject and to determine, based on the one or more pre-operative images, alignment data including alignment of a quadriceps muscle of the subject and adjust, if the alignment data falls outside of a pre-determined alignment range, at least one of the indicated position, orientation or configuration of a component in the surgical plan.

Description

"Surgical System"Technical Field

[0001] The present disclosure relates to knee arthroplasty systems and methods.Background

[0002] Knee replacements involve a surgical procedure to resurface joints typically damaged by arthritis and are some of the most frequently performed and effective surgeries worldwide.

[0003] Arthritis of the knee can be caused by a wide range of contributing factors including weight, age, joint injuries, certain metabolic diseases and gender. Understanding the causes of the wear to the joint may be important in creating an optimal replacement knee.

[0004] Despite a range of customised systems currently available, a large percentage of patients experience a poor outcome following a knee replacement.

[0005] Patellofemoral dysfunction such as patella mal-tracking, patella instability and anterior knee pain are common complications of knee replacement which lead to patient dissatisfaction.

[0006] There is a need for an objective and accurate technique for measuring factors which may affect patient outcomes and to provide a system which optimises a knee replacement procedure to deliver improved patient outcomes.Summary

[0007] The present disclosure relates to a system for determining component positioning, orientation or configuration for a knee arthroplasty system, including: a processor configured to generate a surgical plan, including an indicatedposition, orientation or configuration for a component of the knee arthroplasty system, the processor configured to: receive data including one or more pre-operative images of a subject; determine, based on the one or more pre-operative images, alignment data including alignment of a quadriceps muscle of the subject; adjust, if the alignment data falls outside of a pre-determined alignment range, at least one of the indicated position, orientation or configuration of a component in the surgical plan.

[0008] In another embodiment, the present disclosure provides a method for determining component positioning for a knee arthroplasty system, including: receiving pre-operative data indicative of one or more anatomical structures of a subject; determining, based on the one or more pre-operative images, one or more measurements of a quadriceps muscle relative to a bony structure of a subject; from the one or more measurements, determining a malalignment of the quadriceps muscle; based on the malalignment of the quadriceps muscle, determining an adjustment to a planned implantation of one or more components of the knee arthroplasty system relative to a kinematic alignment and / or a mechanical alignment.

[0009] In a further embodiment, the present disclosure provides a method for determining component positioning for a knee arthroplasty system, including: determining, based on one or more pre-operative images of a subject, a degree of malalignment of a quadriceps muscle of the subject; adjusting, based on the determined degree of malalignment, a planned implantation position and / or orientation of at least one of the one or more components of the knee arthroplasty system.

[0010] In another embodiment, the present disclosure provides a processor configured to generate a surgical plan, including a planned position and orientation for one or more components of the knee arthroplasty system, wherein the processor is further configured to adjust the planned implantation position and / or orientation of at least one of the one or more components of the knee arthroplasty system, based on a malalignment of a quadriceps muscle of the subject.

[0011] In a further embodiment, the present disclosure provides a personalised orthopaedic component for a knee arthroplasty system, the component having a shape or configuration determined by measuring the alignment of a quadriceps muscle of a subject such that if the quadriceps muscle is determined to be malaligned, at least part of the component is adjusted to compensate for the malalignment of the quadriceps muscle.

[0012] In one embodiment, the alignment of the quadriceps muscle may be determined by measuring an alignment of the quadriceps tendon (QT).

[0013] The alignment of the quadriceps muscle may be determined by measuring an alignment of the QT relative to a bony structure of the subject’s anatomy. An example of a bony structure includes at least a part of the femur.

[0014] Several techniques may be used to determine the alignment of the quadriceps muscle using QT alignment.

[0015] One technique includes measuring a translation of the apex of the QT relative to the centre of a trochlear groove of the femur. In this embodiment the translation of the QT is measured on an image such as a CT or MRI and is the distance of translation of the apex of the QT from the centre of the trochlear groove of the femur. The translation distance may be referred to as the QTTG.

[0016] In another example, the alignment of the quadriceps muscle may be determined by measuring the coronal alignment of the QT relative to the mechanical axis of the femur. In this embodiment, angle QTCA may be measured between the mechanical axis of the femur and the apex of the QT as seen on an image. The image may include a CT image or MRI.

[0017] In a further example, the alignment of the quadriceps muscle may be determined by measuring the axial rotation of the QT relative to the centre of the femoral shaft on a single axial slice.

[0018] In a further example, the alignment of the quadriceps muscle may be determined by measuring a quadriceps torsion angle (QMuscle).

[0019] One or more of the techniques described above may be used to determine the alignment of the quadriceps muscle in a subject.

[0020] In one embodiment, the axial rotation of the QT relative to the femoral shaft may be measured by measuring an angle determined from analysis of a CT or MRI image. In one embodiment, the angle may be measured by identifying an apex of the QT on the image and drawing a line to the centre of the femur on the same axial slice of the image. A vertical line perpendicular to the posterior condyles may be drawn on the same image. The axial rotation of the QT may be measured by the angle formed at the intersection of these two lines. The angle may be referred to as QTAx.

[0021] In one embodiment, the alignment data may be the QTAx value.

[0022] The pre-determined alignment range may comprise a range of QTAx values which represent a normal range. The pre-determined QTAx range may be up to approximately 10°. In some embodiments, however, the pre-determined QTAx range may be greater than 10°. The pre-determined QTAx range may be up to 12°, up to 14°, up to 16°, up to 18°, up to 20° or greater than 20°.

[0023] In another embodiment, the pre-determined alignment range may be a range of translation of the QT.

[0024] In a further embodiment, the pre-determined alignment range may be a range of the QTCA.

[0025] In one embodiment, the pre-determined alignment range may be a range of the QMuscle.

[0026] The pre-determined alignment range may be multiple ranges including one or more of a range of QTAx, QTTG, QTCA or QMuscle.

[0027] In an embodiment of the system, the adjustment may include an adjustment of the indicated positioning or orientation of a component of the knee arthroplasty system. The component may be the femoral component.

[0028] The adjustment may include an adjustment of the indicated rotation of the femoral component. The rotation of the femoral component includes internal or external rotation of the femoral component.

[0029] In another embodiment, the adjustment may include an adjustment of the positioning or orientation of a tibial component of the knee arthroplasty system. This includes an adjustment of an indicated rotation of the tibial component. The rotation of the tibial component includes internal or external rotation of the tibial component.

[0030] In further embodiments, the adjustment includes adjustment of any one or more of an indicated lateralisation of the femoral component; medialization of the patella component; coronal alignment of the femur; coronal alignment of the tibia; lateral facetectomy of the patella; or lateral release of the patella.

[0031] In a further embodiment, the adjustment may be to the actual shape and / or configuration of a component. For example, an adjustment may be made to the shape and / or configuration of the femoral component. In an embodiment, an adjustment to a radius of a posterior condyle of the femoral component may be indicated. For example, a medial posterior condyle of the femoral component may be adjusted to have a greater radius than a radius of a lateral posterior condyle. Alternatively, or in addition to the above, the adjustment may include adjustment of the trochlear groove morphology on one or both of the coronal or axial planes of the femoral component. The adjustment may include adjustment of a trochlear groove ridge height.Brief Description of Drawings

[0032] Figure l is a coronal reconstruction CT scan showing the femur, the apex of the quadriceps tendon and the knee of a subject;

[0033] Figure 2 is a CT slice image of a leg of a subject showing the femur and the apex of the quadriceps tendon;

[0034] Figure 3 is a further CT slice image of a leg of a subject showing the femur and the apex of the quadriceps tendon;

[0035] Figure 1 is a CT slice image of a leg of a subject showing the femur and the quadriceps muscles;

[0036] Figure 5a is a CT slice image of a leg of a subject showing the femur and the quadriceps muscles in a patient with normal alignment of the quadriceps muscles;

[0037] Figure 5b is a CT slice image of a leg of a subject showing the femur and the quadriceps muscles in a patient with externally rotated quadriceps muscles;

[0038] Figure 6 is a graph showing the correlation between Quadriceps Muscle Torsional Angle (QMuscle) and Quadriceps Tendon Axial Angle (QTAx)

[0039] Figure 7 is a scatter graph showing a polynomial plot of external rotation of a femoral component of a TKR and the QTAx in a patient group having varying degrees of quadriceps malalignment and exhibiting a KOOS-12 score of greater than 75.Description of Embodiments

[0040] Quadriceps malalignment may be a contributing factor for patellofemoral osteoarthritis such as lateral patellofemoral joint osteoarthritis (LFPFJOA).

[0041] It is therefore desirable to consider the alignment of the quadriceps muscles when planning a surgical procedure such as a total knee replacement (TKR).

[0042] The present disclosure relates to a novel approach to customising a knee replacement compared to conventional systems. Particularly, the present approach measures the actual alignment of the quadriceps muscle. While conventional systemsmay use a measure known as the quadriceps angle (Q angle) as a predictor of patellofemoral instability and anterior knee pain, the Q angle does not measure the alignment (or malalignment if present) of the quadriceps muscles. Rather, the Q angle is a measure of an angle formed between a line from the anterior superior iliac spine (ASIS) or the anterior inferior iliac spine (AXIS) of the pelvis to the centre of the patella and a line between the centre of the patella and the tibial tubercle.

[0043] However, the quadriceps group of muscles is made up of four components: rectus femoris, vastus medialis, vastus intermedius, and vastus lateralis. The rectus femoris portion of the quadriceps muscle is the only portion which attaches to the anterior iliac spine of the pelvis. Vastus medialis, vastus intermedius, and vastus lateralis all attach to the femoral shaft (not the pelvis), as well as to soft tissue attachments in the intermuscular septum and fascia of the thigh.

[0044] One drawback with using the Q angle as a factor in preparing for a TKR procedure is that it is based on bony attachment to the pelvis to which only one quarter of the quadriceps attach. The remaining three quarters of the quadriceps attach to the femur.

[0045] The present inventor has shown that the anatomy of vastus medialis, vastus intermedius, and vastus lateralis are highly variable. One or more of these muscle components may be rotated internally or externally around the femoral shaft which can lead to an abnormal force vector on the patella and thus to patella maltracking, lateral patella osteoarthritis and reduced outcomes after knee replacements. The four components of the quadriceps converge to form the quadriceps tendon (QT) which attaches to the patella. The Q angle does not provide alignment data of the quadriceps muscles.

[0046] Techniques for measuring the true alignment of the quadriceps have been developed.

[0047] QT tendon alignment has been found to be closely correlated with the overall quadriceps muscle alignment and an indicator of the true force vector of the quadriceps as discussed in more detail below.

[0048] The techniques include measuring the alignment of the quadriceps tendon (QT), including measuring: a. The Quadriceps Tendon Coronal Alignment angle (QTCA) b. The translation of the apex of the QT relative to the centre of the trochlear groove (QTTG) c. The Quadriceps Tendon Axial angle (QTAx).

[0049] In addition to measuring QT alignment using the above as a means to determine muscle alignment, the quadriceps torsional angle may also be considered: d. The Quadriceps Muscle Torsion Angle (QMuscle)

[0050] QTCA is the angle between the QT and the mechanical axis 1 of the femur 2 as seen in the coronal plane. It may be measured on a coronal reconstruction as shown in Figure 1. The apex 3 of the QT and the distal point of the trochlear groove 4 are identified. The QTCA is the angle 6 between line 7 drawn between the apex 3 of the QT and the distal point of the trochlear groove 4 and the mechanical axis 1 of femur 2.

[0051] QTTG is shown in the marked up CT slice of Figure 2 and is calculated as the distance of translation 8 of the apex 3 of the QT from intersecting line 9 which extends through the centre of the trochlear groove of the femur 2.

[0052] QTAx is depicted in the marked up CT slice of Figure 3 and is measured by identifying the centre of the apex 3 of the QT and the centre 10 of the femur 2 on the same axial slice and drawing line 11 between these two points. QTAx is the angle 12measured between vertical line 14 perpendicular to the posterior condyle (not shown) and line 11.

[0053] The QTAx shown in Figure 3 is approximately 30° externally rotated. For some surgeries, this may be considered a malalignment of the QT.

[0054] The quadriceps torsion angle or QMuscle is a measure of the degree of rotation of the quadriceps muscles around the shaft of the femur 2. It is most commonly measured at the mid point between hip and knee but can be measured at other points along the femur 2.

[0055] Figure 4 shows an axial slice of a CT scan displaying the QMuscle 15. The quadriceps muscles are shown as 16 and are made up of the rectus femoris, vastus medialis, vastus intermedialis and vastus lateralis. A line 17 is drawn from the anterior aspect of the sartorius muscle 18 to the junction of the lateral intermuscular septum 20. A further line 19 is drawn horizontal to the posterior condyles. The QMuscle 15 is the angle between these two lines.

[0056] The quadriceps muscles 16 shown in Figure 5a are considered normally aligned and the QMuscle 15 is approximately 35°.

[0057] The quadriceps muscles 16 in Figure 5b are abnormally aligned, that is, they are substantially externally rotated relative to the shaft of the femur 2. In this case, the QMuscle 15 is approximately 70°.

[0058] Measurement of the above angles allow for a three dimensional determination of the actual alignment of the components of the quadriceps muscle and the QT rather than assuming the quadriceps muscles run longitudinally along the line of the femur or directly to the pelvis as relied on using the Q angle.

[0059] The three QT alignment techniques noted exhibit a strong correlation with each other and may be used together or individually to provide a measure of QTalignment. Quadriceps tendon malalignment may be highly variable and not correlated with variations in bony anatomy. Demonstrating the variability, in a number of cadavers examined by the present inventor, QTAx was found to range from 44° externally rotated to 42° internally rotated relative to the centre of the femoral shaft was observed. QTCA was found to range from 14° varus to 7° valgus relative to the mechanical axis of the femur and QTTG ranged from -7 varus to +33mm valgus.Study 1 - To determine the association of the alignment of the quadriceps musculature with QT alignment

[0060] 176 Computed Tomography (CT) scans were included in the study. Based on the measured Quadriceps Tendon Axial Angle (QTAx) cases were categorised into “lateralised”, “medialised”, and “normal” groups, summarised below in Table 1.Table 1 - Patient demographic and radiological measurements of each QTAx group

[0061] 10 cases were selected from each group. The Quadriceps Muscle torsional angle (QMuscle) was measured at 7 points along the femur and compared to the QTAx groups.The mean QMuscle measured at each section are summarised on Table 2. The QMuscle at each of the seven levels is compared between the 3 QTAx subgroups. The mean QMuscle across all sections was 47° in the Lateralised Group, 38° in the Normal Group and 31° in the Medialised Group.Table 2: Mean Quadriceps Muscle Torsional Angle (QMuscle) measured at each section across the quadriceps muscle for each Quadriceps Tendon Axial Angle (QTAx) groups.*statistically significant (p<0.05); + = externally rotated, - = internally rotated

[0062] There were differences in QMuscle between the three QTAx groups at all 7 points along the femur, with the lateralised group having the largest mean angle of 46.6° (SD=±7.5°) external rotation across all sections, compared to the normal and medialised groups with external rotations of 37.6° (SD=±3.8°) and 30.6° (SD=±2.9°), respectively (p<0.001).

[0063] A strong correlation (r=0.82, p<0.001) was observed between QTAx and the QMuscle, as shown in Figure 6.Study 2 - To determine if pre-operative QT malalignment (QTM) is associated with worse outcomes following TKR relative to patients without QTM

[0064] 388 patients who had undergone a TKR were selected. Pre-operative CT scans were taken. Following surgery, further CT scans were taken and patient reported outcome measures (PROM) collected. The PROM was collected using the Knee Injury and Osteoarthritis Outcome Score (KOOS-12) questionnaire which was conducted both before and after surgery. The KOOS-12 questionnaire included five patient-relevant dimensions scored separately, including:a. Pain (9 items); b. Symptoms (7 items); c. ADL Function (17 items); d. Sport and Recreation Function (5 items); e. Quality of Life (4 items).

[0065] KOOS-12 scoring was on a 0-100 scale, with 0 representing extreme knee problems and 100 representing no knee problems.

[0066] A review of all the CT scans was conducted and the QTAx determined. A QTAx of greater than 14° was established as a cut-off between a normal quadriceps alignment (below or equal to 14°) and a malalignment of the quadriceps (greater than 14°).

[0067] In the group identified as having quadriceps malalignment, that is with a QTAx greater than 14°, the mean postoperative KOOS-12 was found to be 73.3. In the group identified as having normal quadriceps alignment, that is with a QTAx of below 14°, the mean postoperative KOOS-12 was higher at 80.3.Study 3 - To determine if pre-operative QT malalignment (QTM) is associated with worse outcomes following TKR relative to patients without QTM (using OKS scoring)

[0068] 50 patients who had undergone a TKR were identified as candidates and preoperative CT scans were taken. Following surgery, further CT scans were taken and patient reported outcome measures (PROM) conducted. The PROM was collected using the Oxford Knee Score (OKS), a questionnaire comprising 12 questions to assess pain and physical function. The OKS scoring was on a 0-48 scale, with 0 representing extreme knee problems and 100 representing no knee problems.

[0069] A review of all CT scans in this second study was conducted and the QTAx determined. A QTAx of greater than 14° was established as a cut-off between a normalquadriceps alignment (below or equal to 14°) and a malalignment of the quadriceps (greater than 14°).

[0070] In the group identified as having quadriceps malalignment, that is with a QTAx greater than 14°, the mean postoperative OKS was 35.4 points. In the group identified as having normal quadriceps alignment, that is with a QTAx of below 14°, the mean postoperative OKS was higher at 38.1.

[0071] The mean change in OKS from the pre-operative questionnaire to the postoperative questionnaire was 8.9 points in patients with quadriceps malalignment and 13.9 in patients without quadriceps malalignment.Study 4 - To assess if outcomes of patients with preoperative QTM was improved by adjusting the position of components of the TKR during surgery.

[0072] A review of the post-operative CT scans of each of the 388 patients of Study 2 was conducted. Using a cutoff of a QTAx of 14°, the patient group was divided into those with normal quadriceps alignment (QTAx below or equal to 14°) and those with a malalignment of the quadriceps (QTAx greater than 14°).

[0073] An assessment of the post-operative scans of the patient group with a malalignment of the quadriceps was conducted to determine the positioning of the femoral component of the TKR. The external rotation of the femoral component was measured from each post-operative scan.

[0074] A review of KOOS-12 from the patients in the group identified as having a malalignment of the quadriceps was then conducted and compared to the measurement of external rotation of the femoral component in each case.

[0075] Patients with QTM were analysed in a number of ways to attempt to quantify the effect of femoral component rotation on PROMs. First, applying a KOOS-12 cut-off score based on the median score of 75 points, Further analysis of the group exhibiting agood outcome (75 or higher) showed that there was a significant relationship (r = 0.536, p < 0.001) between the preoperative QTAx angle and the amount of femoral component external rotation required to achieve inclusion in this group (Figure 7). This suggests a dose-dependent relationship between the preoperative QTM and the amount of femoral component rotation required to achieve superior PROMs.

[0076] Second, the same group of patients with QTM was divided into two approximately equal groups based on femoral rotation of greater or less than the median score of 2° from the preoperative posterior condyles. There was a statistically and clinically significant difference in KOOS-12 scores (11.7 points) benefitting the group with more than 2° of external rotation of the femoral component as shown in Table 3 below.Table 3Abbreviations: ADL, activities of daily living; Cl, confidence interval; EQ-VAS, EuroQol Visual Analogue Scale; FJS, Forgotten, Joint, Scale; KOOS, Knee Injury and Osteoarthritis Outcome Score; PROM, patient- reported outcome; QoL, quality of life; QTM, quadriceps tendon malalignment

[0077] This supports the assertion that QTM pathophysiology can be corrected or accommodated by altering the rotational alignment of at least one component of a TKR such as the femoral component to compensate for the deformity.

[0078] The present disclosure relates to a system and method for determining component positioning, orientation or configuration for a knee arthroplasty system including adjusting at least one indicated position, orientation or configuration of a component in a surgical plan. Data relating to the alignment of the quadriceps as set out above may be used to determine any adjustments that may be required during a surgical procedure.

[0079] In one embodiment, an indicated adjustment may include an indication to consider a femoral component external rotation in cases where the QTAx of a patient is greater than 14°.

[0080] In some embodiments, the QTAx may be 14°, 15°, 16°, 17°, 18°, 19°, 20° or higher. In some cases, the QTAx of a patient may be 21°, 22°, 23°, 24°, 25°, 26°, 27°, 28°, 29°, 30° or higher.

[0081] The predetermined alignment range may differ for different patients and different surgeries.

[0082] The indicated femoral component rotation may be in the range of from 1.0° to 5.0° or higher. For example, 1.0°, 1.5°, 2.0°, 2.5°, 3.0°, 4.0°, 5.0° or higher.

[0083] In one embodiment, the indicated adjustment includes an indication to consider a femoral component external rotation of approximately 2.0° in cases where the QTAx is approximately 15°.

[0084] In one embodiment, for each degree of QTAx greater than 15°, the indicated adjustment may be to externally rotate the femoral component by between approximately 0.03° and 0.1°.

[0085] In one embodiment, the indicated adjustment includes an indication to consider a femoral component external rotation of approximately 4.0° or greater in cases where the QTAx is approximately 40°.

[0086] Rather than basing an adjustment on a linear relationship there may be benefit to a greater external rotation of the femoral component in patients with a relatively moderate malalignment for example of between approximately 20° to 27° as shown in Figure 7.

[0087] Similarly, from the results plotted in Figure 7, it may not be significantly beneficial to increase the external rotation of the femoral component beyond approximately 4.0° in patients with malalignment of greater than 27°.

[0088] In one example, if a patient has a QTAx ranging from approximately 15° to 20°, the indicated adjustment may be to externally rotate the femoral component by between 2.0° and 3.5°. The indicated adjustment may be to rotate the femoral component by 2.0°, 2.1°, 2.2°, 2.3°, 2.4°, 2.5°, 2.6°, 2.7°, 2.8°, 2.9°, 3.0°, 3.1°, 3.2°, 3.3°, 3.4°, or 3.5°.

[0089] In a further example, if a patient has a QTAx ranging from approximately 20° to 27°, the indicated adjustment may be to externally rotate the femoral component by between 3.6° to 4.0°. The indicated adjustment may be to rotate the femoral component by 3.6°, 3.7°, 3.8°, 3.9°, or 4.0°.

[0090] In another example, if a patient has a QTAx greater than 27°, the indicated adjustment may be to externally rotate the femoral component by between 4.0° to 4.5°. The indicated adjustment may be to rotate the femoral component by 4.0°, 4.1°, 4.2°, 4.3°, 4.4°, or 4.5°.

[0091] In one study, the recommended guidelines are provided in Table 4.Table 4

[0092] While the above studies relate to adjusting the femoral component by external rotation, it is envisaged that other adjustments to other components of the TKR may be made instead, or in addition to, the femoral component.

[0093] For example, the tibial component of the knee arthroplasty system may also be adjusted in line with, or independently of, the adjustment of the femoral component. For example, external rotation of the tibial component may be proposed to be increased as the QTAx increases.

[0094] The data discussed in the embodiments above relates to TKR procedures using the SAIPH® Knee System from MatOrtho. It is envisaged that the relationship between QTAx and the degree of external indication will vary depending upon the brand of components used.

[0095] If malalignment of the quadriceps muscle is identified, in addition to adjusting the rotation of the femoral and / or tibial components of a TKR, other adjustments maybe made separately, or in addition to these adjustments. Examples include the adjustment of any one or more of lateralisation of the femoral component, medialization of the patella component, coronal alignment of the femur, coronal alignment of the tibia, lateral facetectomy of the patella or lateral release of the patella.

[0096] The adjustment may include an adjustment of an indicated configuration of the component. For example the configuration of the femoral component. In one embodiment the indicated adjustment may be to adjust the configuration of the radius of a posterior condyle of the femoral component. In one embodiment, if malalignment is observed, the indicated adjustment may be to adjust a medial posterior condyle of the femoral component to have a greater radius than a radius of a lateral posterior condyle.

[0097] The adjustment includes adjustment of trochlear groove morphology on one or both of the coronal or axial planes of the femoral component. In one embodiment the adjustment includes adjustment of a trochlear groove ridge height.

[0098] It will be appreciated by persons skilled in the art that numerous variations and / or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1. A system for determining component positioning, orientation or configuration for a knee arthroplasty system, including: a processor configured to generate a surgical plan, including an indicated position, orientation or configuration for a component of the knee arthroplasty system, the processor configured to: receive data including one or more pre-operative images of a subject; determine, based on the one or more pre-operative images, alignment data including alignment of a quadriceps muscle of the subject; adjust, if the alignment data falls outside of a pre-determined alignment range, at least one of the indicated position, orientation or configuration of a component in the surgical plan.

2. The system of claim 1, wherein the alignment of the quadriceps muscle is determined by measuring an alignment of the quadriceps tendon.

3. The system of claim 2, wherein the alignment of the quadriceps tendon is determined by measuring a translation of the apex of the quadriceps tendon relative to the centre of a trochlear groove of the femur.

4. The system of claim 2, wherein the alignment of the quadriceps tendon is determined by measuring the coronal alignment of the quadriceps tendon relative to the mechanical axis of the femur.

5. The system of claim 2, wherein the alignment of the quadriceps tendon is determined by measuring the axial rotation of the quadriceps tendon relative to the centre of the femoral shaft.

6. The system of claim 1 wherein the alignment of the quadriceps muscle is determined by measuring the quadriceps torsion angle.

7. The system of any one of the preceding claims, wherein the alignment of the quadriceps muscle is determined by measuring two or more of:(i) a translation of the apex of the quadriceps tendon relative to the centre of a trochlear groove of the femur;(ii) the coronal alignment of the quadriceps tendon relative to the mechanical axis of the femur;(iii) the axial rotation of the quadriceps tendon relative to the centre of the femoral shaft; or(iv) the quadriceps torsion angle.

8. The system of claim 5, wherein the pre-determined alignment range comprises up to 10° axial rotation of the quadriceps tendon relative to the shaft of the femur.

9. The system of claim 5, wherein the pre-determined alignment range comprises up to 12° axial rotation of the quadriceps tendon relative to the shaft of the femur.

10. The system of claim 5, wherein the pre-determined alignment range comprises up to 14° axial rotation of the quadriceps tendon relative to the shaft of the femur.

11. The system of claim 5, wherein the pre-determined alignment range comprises up to 20° axial rotation of the quadriceps tendon relative to the shaft of the femur.

12. The system of any one of the preceding claims, wherein one or more preoperative images of a subject include CT or MRI images.

13. The system of any one of the preceding claims, wherein the adjustment includes an adjustment of the indicated positioning or orientation of a femoral component of the knee arthroplasty system.

14. The system of claim 13, wherein the adjustment includes an adjustment of the indicated rotation of the femoral component.

15. The system of claim 14, wherein the rotation of the femoral component includes external rotation.

16. The system of any one of the preceding claims, wherein the adjustment includes an adjustment of the positioning or orientation of a tibial component of the knee arthroplasty system.

17. A method for determining component positioning for a knee arthroplasty system, including: receiving pre-operative data indicative of one or more anatomical structures of a subject; determining, based on the one or more pre-operative images, one or more measurements of a quadriceps muscle; from the one or more measurements, determining a malalignment of the quadriceps muscle; based on the malalignment of the quadriceps muscle, determining an adjustment to a planned implantation of one or more components of the knee arthroplasty system relative to a kinematic alignment and / or a mechanical alignment.

18. The method of claim 17, wherein one or more measurements of a quadriceps muscle includes measuring an alignment of the quadriceps tendon relative to the femur.

19. The method of claim 18, wherein determining the one or more measurements of a quadriceps muscle includes measuring a translation of the apex of the quadriceps tendon relative to the centre of a trochlear groove of the femur.

20. The method of claim 18, wherein determining the one or more measurements of a quadriceps muscle includes measuring the coronal alignment of the quadriceps tendon relative to the mechanical axis of the femur.

21. The method of claim 18, wherein determining the one or more measurements of a quadriceps muscle includes measuring the axial rotation of the quadriceps tendon relative to the centre of the femoral shaft on a single axial slice.

22. The system of claim 17, wherein the alignment of the quadriceps muscle is determined by measuring the quadriceps torsion angle.

23. The system of any one of claims 18-22, wherein the alignment of the quadriceps muscle is determined by measuring two or more of:(i) a translation of the apex of the quadriceps tendon relative to the centre of a trochlear groove of the femur;(ii) the coronal alignment of the quadriceps tendon relative to the mechanical axis of the femur;(iii) the axial rotation of the quadriceps tendon relative to the centre of the femoral shaft; or(iv) the quadriceps torsion angle.

24. The method of claim 21, wherein the step of determining malalignment of the quadriceps muscle includes determining an axial rotation of the quadriceps tendon greater than 10°.

25. The method of claim 21, wherein the step of determining malalignment of the quadriceps muscle includes determining an axial rotation of the quadriceps tendon greater than 12°.

26. The method of claim 21, wherein the step of determining malalignment of the quadriceps muscle includes determining an axial rotation of the quadriceps tendon greater than 14°.

27. The method of claim 21, wherein the step of determining malalignment of the quadriceps muscle includes determining an axial rotation of the quadriceps tendon greater than 20°.

28. The method of claim 21, wherein the step of determining malalignment of the quadriceps muscle includes determining an axial rotation of the quadriceps tendon greater than 30°.

29. The method of claim 21, wherein the step of determining malalignment of the quadriceps muscle includes determining an axial rotation of the quadriceps tendon greater than 40°.

30. The method of any one of claims 17 to 29, wherein one or more pre-operative images of a subject include CT or MRI images.

31. The method of any one of claims 17 to 30, wherein the adjustment includes an adjustment of the indicated positioning or orientation of a femoral component of the knee arthroplasty system.

32. The method of claim 31, wherein the adjustment includes an indicated rotation of the femoral component.

33. The method of claim 32, wherein the rotation of the femoral component includes external rotation.

34. A method for determining component positioning for a knee arthroplasty system, including: determining, based on one or more pre-operative images of a subject, a degree of malalignment of a quadriceps muscle of the subject; adjusting, based on the determined degree of malalignment, a planned implantation position and / or orientation of at least one of the one or more components of the knee arthroplasty system.

35. A processor configured to generate a surgical plan, including a planned position and orientation for one or more components of the knee arthroplasty system, wherein the processor is further configured to adjust the planned implantation positionand / or orientation of at least one of the one or more components of the knee arthroplasty system, based on a malalignment of a quadriceps muscle of the subject.

36. A personalised orthopaedic component for a knee arthroplasty system, the component having a shape or configuration determined by measuring the alignment of a quadriceps muscle of a subject such that if the quadriceps muscle is determined to be malaligned, at least part of the component is adjusted to compensate for the malalignment of the quadriceps muscle.

37. The personalised orthopaedic component of claim 36, wherein the component is the femoral component.

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