Aims. Sagittal plane imbalance (SPI), or asymmetry between extension and flexion gaps, is an important issue in total knee arthroplasty (TKA). The purpose of this study was to compare SPI between kinematic alignment (KA), mechanical alignment (MA), and functional alignment (FA) strategies. Methods. In 137 robotic-assisted TKAs, extension and flexion stressed gap laxities and bone resections were measured. The primary outcome was the proportion and magnitude of medial and lateral SPI (gap differential > 2.0 mm) for KA, MA, and FA. Secondary outcomes were the proportion of knees with severe (> 4.0 mm) SPI, and resection thicknesses for each technique, with KA as reference. Results. FA showed significantly lower rates of medial and lateral SPI (2.9% and 2.2%) compared to KA (45.3%; p < 0.001, and 25.5%; p < 0.001) and compared to MA (52.6%; p < 0.001 and 29.9%; p < 0.001). There was no difference in medial and lateral SPI between KA and MA (p = 0.228 and p = 0.417, respectively). FA showed significantly lower rates of severe medial and lateral SPI (0 and 0%) compared to KA (8.0%; p < 0.001 and 7.3%; p = 0.001) and compared to MA (10.2%; p < 0.001 and 4.4%; p = 0.013). There was no difference in severe medial and lateral SPI between KA and MA (p = 0.527 and p = 0.307, respectively). MA resulted in thinner resections than KA in medial extension (mean difference (MD) 1.4 mm, SD 1.9; p < 0.001), medial flexion (MD 1.5 mm, SD 1.8; p < 0.001), and lateral extension (MD 1.1 mm, SD 1.9; p < 0.001). FA resulted in thinner resections than KA in medial extension (MD 1.6 mm, SD 1.4; p < 0.001) and lateral extension (MD 2.0 mm, SD 1.6; p < 0.001), but in thicker medial flexion resections (MD 0.8 mm, SD 1.4; p < 0.001). Conclusion. Mechanical and kinematic alignment (measured resection techniques) result in high rates of SPI. Pre-resection angular and translational adjustments with functional alignment, with typically smaller distal than posterior femoral resection, address this issue. Cite this article: Bone Jt Open 2024;5(8):681–687

Abstract. Objectives. The objective of this proof of concept study was to explore whether some total hip arthroplasty (THA) patients with well-functioning implants achieve normal sagittal plane hip kinematics during walking gait. Methods. Sagittal plane hip kinematics were recorded in eleven people with well-functioning THA (71 ± 8 years, Oxford Hip Score = 46 ± 3) and ten healthy controls (61 ± 5 years) using a three-dimensional motion capture system as they walked over-ground at a self-selected velocity. THA patients were classified as high- or low-functioning (HF and LF, respectively) depending on whether the mean absolute difference between their sagittal plane hip kinematics was within one standard deviation of the control group (5.4°) or not. Hedge's g effect size was used to compare the magnitude of the difference from the control group for the HF and LF THA groups. Results. Five THA patients were identified as HF and 6 as LF. The mean absolute difference in sagittal plane hip kinematics between the THA groups and the control group was on average 6.2° larger for the LF THA patients compared to the HF, with this difference associated with a large effect size (g = 1.84). Conclusions. The findings of this study challenge the findings of previous work which suggests THA patients do not achieve normal sagittal plane hip kinematics. Five patients were classified as HR and achieved motion patterns that were on average within the variance of the asymptomatic control group, suggesting normative sagittal plane hip kinematics. Understanding why some THA patients achieve motion patterns more comparable to healthy controls than others would help to develop means of maximising functional recovery, and potentially enhance both patient quality of life and implant survivorship through more normal loading of the implant

The long-term survival of total knee arthroplasty (TKA) has been well established; however, functional outcome remains inconsistent. More normal postoperative TKA kinematics have been shown to produce better knee function. Improved kinematics can be obtained by using implants with optimised surface geometry. Hence a TKA with an appropriate surface geometryis likely to provide superior long-term functional outcome. The Advance-Medial Pivot TKA (Wright Medical) is a fixed bearing prosthesis with a conforming medial compartment and a non-conforming (flat on flat) lateral compartment. This surface geometry is designed with the intention of replicating the normal knee motion of sliding or pivoting medially and rolling back laterally. Aim: To investigate the sagittal plane kinematics of Advanced Medial Pivot Knee and compare with those of “flat on flat” fixed bearing TKA and normal knees. 18 patients who had undergone primary TKA for osteoarthritis were recruited at an average of 18 months post operation. These patients performed flexion and extension exercises against gravity and a step up exercise. Video fluoroscopy of these activities was used to obtain the patellar tendon angle (PTA). This is a previously validated method for assessing sagittal plane kinematics of a knee joint. The kinematic profile of the Advance Medial Pivot Knee was compared to the profile of 14 normal knees and 30 flat on flat, fixed bearing TKA’s. The sagittal plane kinematics of the Advance TKA differed from the normal knees. However, similarly to normal knees, a linear relationship was observed between PTA and knee flexion angle throughout knee flexion range. The kinematics of the Medial Pivot Knee were similar to normal when the knee was in a highly flexed position. Functional plane kinematics of the Advance Medial Pivot TKA appear to meet the design criteria in that a linear relationship between PTA and flexion angle is maintained. Further work is required to establish if these improved sagittal plane kinematics translate into improved functional outcome

Introduction. Radiological inclination (RI) is determined in part by operative inclination (OI), which is defined as the angle between the cup axis or handle and the sagittal plane. In lateral decubitus the theatre floor becomes a surrogate for the pelvic sagittal plane. Critically at the time of cup insertion if the pelvic sagittal plane is not parallel to the floor either because the upper hemi pelvis is internally rotated or adducted, RI can be much greater than expected. We have developed a simple Pelvic Orientation Device (POD) to help achieve a horizontal pelvic sagittal plane. The POD is a 3-sided square with flat footplates that are placed against the patient's posterior superior iliac spines following initial positioning (figure 1). A digital inclinometer is then placed parallel and perpendicular to the patient to give readings of internal rotation and adduction, which can then be corrected. Methods. A model representing the posterior aspect of the pelvis was created. This permitted known movement in two planes to simulate internal rotation and adduction of the upper hemi pelvis, with 15 known pre-set positions. 20 participants tested the POD in 5 random, blinded position combinations, providing 200 readings. The accuracy was measured by subtracting each reading from the known value. Results. 2 statistical outliers were identified and removed from analysis. The mean adduction error was 0.73°. For internal rotation, the mean error was −0.03°. Accuracy within 2.0° was achieved in 176 of 190 (93%) of readings (Table 1). The maximum error was 3.6° for internal rotation and 3.1° for adduction. Conclusion. In a model pelvis the POD provided an accurate and reproducible method of achieving a horizontal sagittal plane. Applied clinically, this simple tool has the potential to reduce the high values of RI sometimes seen following THA in lateral decubitus. For any figures and tables, please contact the authors directly

Functional outcome after patellofemoral joint replacement (PFA) for osteoarthritis remains inconsistent. It is believed that functional outcome for joint replacement is dependent upon postoperative joint kinematics. Minimal disruption of the native joint, as in PFA, should produce more normal kinematics and improved outcome. No previous studies have examined joint kinematics after isolated PFA. Aim: To investigate the sagittal plane kinematics of patellofemoral replacement and compare with the normal knee. Twelve patients who had undergone successful PFA at least two years previously were recruited. Patients performed flexion/extension against gravity, and a step up. Video fluoroscopy of these activities was used to obtain the Patellar Tendon Angle (PTA), the angle between the long axis of the tibia and the patella tendon, as a function of knee flexion. This is a previously validated method of assessing sagittal plane kinematics of a knee joint. The kinematic profile of the PFA joints was compared to the profiles for fourteen normal knees. Overall, the kinematic plot obtained for PFA reflected similar trends to that for normal knees; but the PTA was slightly but significantly increased throughout the entire range of flexion (two degrees). This is equivalent to an average displacement of the lower pole of the patella of 1.5mm. Sagittal plane knee kinematics after PFA are much more normal than after TKR and this should give improved functional outcome. The observed increase in PTA through range may result from increased patella thickness or a shallow trochlear groove and may influence patellofemoral contact forces

Introduction. Flexion instability of the knee accounts for, up to, 22% of reported revisions following TKA. It can present in the early post-operative phase or present— secondary to a rupture of the PCL— in the late post-operative phase. While most reports of instability occur in conjunction with cruciate retaining implants, instability in a posterior-stabilized knee is not uncommon. Due to the prevalence of revision due to instability, the purpose of constructing the following techniques is to utilize intraoperative sensors to quantify flexion gap stability. Methods. 500 posterior cruciate-retaining TKAs were performed between September 2012 and April 2013, by four collaborating surgeons. All surgeons used the same implant system, compatible with a microelectronic tibial insert with which to receive real-time feedback of femoral contact points and joint kinetics. Intraoperative kinematic data, as reported on-screen by the VERASENSE™ knee application, displayed similar loading patterns consistent with identifiable sagittal plane abnormalities. These abnormalities were classified as: “Balanced Flexion Gap,” “Flexion Instability” and “Tight Flexion Gap.” All abnormalities were addressed with the techniques described herein. Results. Balanced Flexion Gap. Flexion balance was achieved when femoral contact points were within the mid-posterior third (Figure 1) of the tibial insert, symmetrical rollback was seen through ROM, intercompartmental loads were balanced, and central contact points displayed less than 10 mm of excursion across the bearing surface during a posterior drawer test. Flexion Instability. The femoral contact point tracking option dynamically displayed the relative motion of distal femur to the proximal tibia during the posterior drawer test, and through range of motion. Excessive excursion of the femoral contact points across the bearing surface, and femoral contact points translating through the anterior third of the tibial trial, was an indication of laxity in the PCL. Surgical correction requires use of a thicker tibial insert, anterior-constrained insert, or a posterior-stabilized knee design (Figure 2). Tight Flexion Gap. Excessive tension in the PCL was displayed during surgery via femoral contact points and excessive high pressures in the posterior compartment during flexion. When a posterior drawer test was applied no excursion of the femoral tibia contact point was seen. Excessively high loading in the posteromedial compartment was corrected through recession of the PCL using an 19 gauge needle or 11 blade. Additional tibial slope was added when excessive loads were seen in both compartments (Figure 3). Discussion. Flexion gap instability, or excessive PCL tension, is a common error resulting in poor patient outcomes and early revision surgery. The techniques described, utilized intraoperative sensor data to address sagittal plane abnormalities in a quantified manner. By using technology to guide the surgeon through appropriate sagittal plane correction, the subtleties in soft-tissue imbalance or suboptimal bone cuts can be accounted for, which otherwise may be overlooked by traditional methods of subjective surgeon “feel.” Longer clinical follow-up of these patients will be necessary to track the outcomes associated with quantifiable sagittal plane balance

The aim of this study was to investigate if the rotational axis of normal human shoulders moves during flexion in the sagittal plane. Twenty four shoulders were measured in twelve normal volunteers, aged 25-42, height range 1.65-1.88 m and weight range 63–120 Kg. Each subject had surface markers placed on their iliac crests, mastoid processes and upper arms. Joint movement was video recorded as shoulders were actively flexed and extended in the sagittal plane. For each joint, a typical flexion sweep was selected and replayed into a computerised imaging system, where still frames were captured at 20 degree intervals from 20 to 120 degrees. These images were analysed to extract the co-ordinates of each marker. The coordinates were then processed to determine the Instant Centres of Rotation (ICR) for each angle of flexion. These ICR’s were then plotted to derive the Rotational Axis Pathway (RAP) for each shoulder joint. The results indicate that throughout the flexion arc, the rotational axis is located in the region of the humeral head. At the start of the arc the rotational axis is in the anterio-superior part of the shoulder joint. As the shoulder flexes forward the rotational axis moves posteriorly following a curved pathway. In 18 cases the RAPs moved posterio-inferiorly and in six cases the RAPs moved posterio-superiorly. The pathways can be quantified in terms of their curved pathway lengths and the displacements of their end points from their start points. In the case of the 18 posterio-inferior pathways, the mean pathway length was 98.3 mm (SD=31.5) and the mean posterior/inferior displacements were 59.6 mm (SD=34.7) and 43.2 mm (SD=24.6) respectively. In the case of the 6 posterior-superior pathways, the mean pathway length was 109.4 mm (SD=40.2) and the mean posterior/ superior displacements were 94.7 mm (SD=43.9) & 20.9 mm (SD=11.1) respectively. The variation in inferior-superior displacement of the axis may be due to normal variations in scapula movement during forward flexion. This investigation indicates that in normal subjects, the rotational axis moves posteriorly during flexion

The goal of treatment in scoliosis is not only curve correction. Restoration of normal sagittal alignment is also very important. Methods describing sagittal balance are various, they include measurement of thoracic kyphosis and lumbar lordosis, alignment of thoracolumbar junction and distance between plumb line from C7 and sacral bone. Goals of work:. Evaluation the sagittal plane alignment after surgery in idiopathic scoliosis, type 5 and 6 according to Lenke classification;. Establishing risk factors of bad end result. Material consists of 52 patients. The mean age at the time of surgery was 16 years with the follow up time of 4 years. There were 29 patients in first group, with Lenke type 5 and 23 patients in the second group, with type 6. The Cobb angle of structural curves was in Lenke 5 group 52.5o ± 5.9 and in Lenke 6 group − 54.4o ± 8,4 in thoracic spine and 66.3o ± 11.9 in lumbar spine. Preoperative thoracic kyphosis was 20.9o ± 6.9 and 29.3o ± 15.5. Lumbar lordosis was 42.5o ± 11.4 and 35.9o ± 11.4. Thoracolumbar junction was almost straight in first group; Th12-L2 angle was 0o ± 6.7 and slight kyphotic in second group: 4o ± 8.1. All the patients underwent posterior fusion with derotational instrumentation. Radiological assessment was performed using postero-anterior and lateral radiograms. Own scale of treatment result evaluation was introduced. Results: During control examination the thoracic kyphosis was 30.1o ± 7.8 and 27.8o ± 9.4 and lumbar lordosis was 40.3o ± 12.3 and 35.7o ± 9.9. During follow-up, the mean thoracolumbar junction angle was −4.4o ± 9.6 and −7.9o ± 9.9. Proper alignment of thoracolumbar junction was observed in 24 patients (82.8%) from first group and 21 patients (91%) from the second. Good results in sagittal plane were noted in 22 cases (76%) from Lenke 5 group and 21 cases (91%) from Lenke 6 group. The presence of pedicle srews in lumbar spine was bound with significantly better end result. Smaller lordosis, greater probability of bad result. Kyphotic thoracolumbar junction before surgery was connected with greater risk of bad result. The level of lower end of fusion was significantly important in pre-dicticting end result. Conclusions:. Own method of describing result in sagittal plane allows better assessment of sagittal balance;. There are several factors influencing end result in sagittal plane in scoliosis surgery;. The best indicator of bad sagittal result is improper alignment of thoracolumbar junction

To determine extent of correction in spinal osteotomy for fixed sagittal plane deformity. Radiographic retrospective cohort analysis using standardised standing whole spine radiographs. Level III evidence. 24 patients (14 females/10 males, av. 53.6 yrs) with sagittal plane deformity due to either ankylosing spondylitis (4), idiopathic (12), congenital (1), tumour (2), infectious (1), or posttraumatic (4) aetiologies. Max. 4 yrs follow up. Sagittal balance, lumbar lordosis correction, osteotomy angle, pelvic indices. Chevron (3), pedicle subtraction (17), and vertebral column resection (4) osteotomies were performed with the majority at L3 (9) and L2 (8). The C7-S1 sagittal vertical axis demonstrated a preoperative decompensation averaging 12.0 cm (range -7 to 37) with 55% of patients achieving normal sagittal balance postoperatively. Lumbar lordosis increased from 28.9° (range -28 to 63) to 48.9° (range 12 to 69) (22.3° av. correction). L3 osteotomy angle was largest, average 31° (range, 16 to 47). There were 11 complications comprising; major (1) and minor (1) neurological, junctional kyphosis (3), metalwork problems (2), dural tear (2) and infection (2). Four patients required additional surgery at latest follow-up. Technical outcome was good 11(50%), fair 8(36%), poor 3(14%). Spinal osteotomy is a very effective technique to correct fixed sagittal imbalance and provide biomechanical stability. The high complication rate mandates a careful assessment of the risk/benefit ratio before undertaking what is a major reconstructive procedure. Most patients are satisfied, particularly when sagittal balance is achieved

The palpation of the controlateral iliac spinae remains a major hurdle to the success of navigation in lateral position. Several studies are seeking for alternative landmarks to compute the anterior pelvic plane (APP). Up to now, none of those methods have been used in clinical routine. Ultrasound navigation offers a great potential to identify new bony landmarks. The tubercles of the lower lumbar spine and the symphysis can easily be imaged. Those points define a sagittal plane, that can be used as a symmetry plane to compute a virtual controlateral spinae from the acquired colateral spinae. A virtual pelvic plane can then be computed. The objective of this study was to check the accuracy and reproducibility of this virtual anterior pelvic plane. 6 hips (3 left, 3 right) from 4 cadavers (mean BMI 22,6; range 19,5–26,7) embalmed with glycerol and alcohol were used for this study. All anatomic landmarks were acquired with the OrthoPilot® Ultrasound navigation system. One experienced surgeon acquired the reference APP with the cadavers lying supine. The cadavers were then placed in lateral position. Two experienced surgeons acquired 6 times following landmarks: 3 lower lumbar tubercles, 3 sacral tubercles (see Figure 1), the posterior spines, the symphysis and the colateral iliac spine. Several sagittal planes were computed using all points (least square plane) and all possible combinations between one symphysis point, one lower lumbar tubercle point (L5, L4 or L3), and one sacral tubercle point (S2 or S1). The angular error of the resulting virtual APP to the reference APP was computed. For each cadaver, an error map was computed to visualize the error of the virtual APP with respect to the height of the used sacral and lumbar tubercles along the spine. The reference APP was acquired with a good reproducibility: the deviation between each acquisition to the mean of all acquisitions was smaller than 1° (except for cadaver 2 right side, the deviation reached 2 ° in the frontal plane). As some sacral and lumbar points were mixed during the acquisition, the line joining the posterior spines was used to separate the sacral from the lumbar points. The mean errors and standard deviations were comparable between operators. The least square plane computed with all points strongly depended on the cadaver positioning : for the same cadaver, the mean error reached 0°on the left side and 8° on the right side. More constant results were obtained by using a combination of 3 points. 5 outliers were identified and removed as they clearly corresponded to erroneous acquisitions on bad quality images. After having removed those outliers, the mean error ranged between 2° and 5° and the standard deviation between 1° and 3°. The best combination of points was a point on the symphysis, the lowest sacral tubercle (S2) and the lowest lumbar tubercle (L5). This study shows that the symphysis, the lower lumbar and sacral tubercles can be used to define a sagittal plane and thereby define a virtual anterior pelvic plane. Outliers should be suppressed by taking special care to the image quality and by adding a guided ultrasound functionality: visualizing the resulting sagittal plane on the ultrasound picture would enable the surgeon to easily control the accuracy of his acquired plane. The next steps consist in checking the feasibility in a clinical set-up

Introduction. Maintaining posterior stability in total knee arthroplasty (TKA) may be achieved by using a posterior stabilized TKA, retaining and balancing the posterior cruciate ligament (PCL) using a traditional cruciate-retaining design (CR), or by increasing the sagittal plane conformity of the tibial insert. In the latter case, stability is achieved by the addition of an anterior buildup on the tibial polyethylene creating the so-called “anterior stabilized” (AS) design. We hypothesized that using an AS tibial insert would provide similar function and survivorship as compared to using a more traditional CR bearing when the PCL is either recessed or balanced. Methods. Between 2004 and 2016, 1,731 modular CR TKAs were implanted in 1,509 patients using the same CR TKA design. The diagnosis was osteoarthritis in 98%. 58% of patients were female. Average age of 64.9 years. Within this group, 868 TKAs (50.1%) had a standard CR tibial bearing (3-degree posterior slope and no posterior lip) implanted (CR-S). 480 TKAs (27.8%) had a lipped CR modular tibial bearing (2.5 mm elevated posterior lip) implanted (CR-L). Starting in 2013, 383 TKAs (22.1%) were implanted with an AS modular tibial bearing (9–11 mm anterior lip and a 5 mm posterior lip). If the PCL was considered non-functional or absent, an AS bearing was placed. If the PCL was considered functional, a standard bearing or lipped bearing was used. Clinical and radiographic analysis was performed according to the Knee Society (KS) grading system. The most recent clinical and radiographic evaluation was used for post-operative analysis. The average follow-up in the entire cohort of TKAs was 5.5 years (range 2 to 14.3 years). Kaplan-Meier analysis was used to determine prosthesis survivorship with failure defined as aseptic loosening of the prosthesis (with or without revision) or tibial insert exchange. Results. At final follow-up, there were no significant differences in knee flexion, pain, function, or stair scores. Walking scores were significantly lower in the AS group. Posterior instability was higher in the CR-S group, whereas the manipulation rate was highest in the CR-L group (1.7% versus 1.3% and 0% in the CR-S and AS groups, respectively). Kaplan-Meier survivorship at five years, excluding infection, demonstrated no significant difference between the three groups (CR-S, CR-L, and AS tibial insert groups, 99% 100% and 99% respectively). Conclusion. When the PCL is considered non-functional at operation, the AS insert provided similar final flexion, function, stair score, and five-year survivorship when compared to using the standard and lipped CR tibial insert when the PCL was balanced. Using an ultra-congruent AS dished tibial component appears to be a reasonable option when the PCL is completely released or found deficient at operation. For figures, tables, or references, please contact authors directly

Purpose: Femoral roll causes the sagittal plane axis of the knee to move posteriorly and anteriorly with flexion and extension. The aim of this study was to measure this movement with a surface marker imaging system and assess the effect of Anterior Cruciate Ligament (ACL) deficiency on the Sagittal Axis Pathway (SAP) of the knee. Method: Twelve normal and fourteen unilateral ACL deficient subjects were video recorded as they flexed and extended their knees in the sagittal plane. Video stills were captured at 150 intervals from 90o flexion to full extension. An imaging system was then used to extract the co-ordinates of leg markers from each still. These co-ordinates were then processed to derive the SAP for each knee throughout its range of movement. Results: Pooling all the normal results together (24 bilateral + 14 unilateral = 38 knees), it was found that a 90° knee extension caused the sagittal axis to displace anteriorly with a mean value of 20.0mm (SD=7.8). In comparison the 14 ACL deficient knees were found to have a mean anterior displacement of 9.2 mm (SD=8.0). A bilateral comparison of the 12 pairs of normal knees showed no significant difference between left and right sides (paired-t, p=0.99). However, a bilateral comparison of the 14 unilateral ACL deficient patients showed a significant difference between normal and injured sides (paired-t, p=0.00025). In this group, the normal knees axis at full extension had a mean location 28.9mm (SD=8.8) posterior to the front of the tibial plateau. In comparison the injured knees axis has a mean location 37.8 mm (SD=8.5) posterior to the front of the tibial plateau. Again, this was highly significant (paired-t, p=0.0001). Conclusion: These results indicate that normal knees have a mean forward roll of 20 mm for a 90° knee extension. In comparison ACL deficient knees have a reduced roll of 9.2 mm which occurs at the rear of the joint. This reduction in roll is consistent with the abnormal ligament biomechanics

Experience has shown that oblique fractures can be slow to heal and this has been attributed to excess shear at the fracture site. We routinely treat fractures with hybrid external fixation. In previous studies, olive wires placed through the fracture site reduced shear and this has improved healing times. When the fracture is oblique in the sagittal plane, anatomical constraints prevent the use of olive wires and a new solution is required. A sawbone tibia with a distal sagittal plane oblique fracture (70° obliquity) was stabilised with a Sheffield Hybrid Fixator. In a pilot study various methods of fixation were tested and six were chosen for further testing. Since the pull-out strength of threads in the plastic bone was poor, olive wires cut behind the olive were used as a mechanically equivalent model for the push-pull system. Seventy degree steerage pins could not be used so 25° pins were tested instead. Cyclic compressive forces (at 10mm/min) of up to 200N axially and in four off-axis positions were applied using a universal testing machine. Fracture site linear motion in three dimensions was measured using an inter-fragmentary motion device, sampled at 100Hz. A standard frame was tested before and after each adaptation and all six methods were applied sequentially to each model. The results suggest that: I) Arched wires are effective especially under greater bends, 2) Push-pull wires are effective and provide a minimally disruptive solution, 3) Steerage pins are effective especially at steeper obliquities but this may not always be practical, and 4) Placing a half pin in the distal fragment is beneficial but less effective than the use of 2 transverse half pins acting in a compression system (Hutson technique)

The footplate in the current available TDR is flat without any allowance for endplate concavity in the sagittal plane. To assess the morphology of the endplates of the lower lumbosacral in the sagittal plane, and to identify the frequently occurring shape patterns of the end plates at each level. Retrospective Study. 200 consecutive magnetic reasonance imaging (MRI) scans of patients between the age of 30 and 60 years were analysed. In each endplate, the anteroposterior width, the height of concavity of the endplate, and the distance of the summit from the anterior vertebral body margin were noted. The shape of the endplate was noted as oblong (o) if the curve was uniform starting from the anterior margin and finishing at the posterior margin, eccentric (e) if the curve started after a flat portion at the anterior border and then curving backwards, and flat (f) if there is no curve in the sagittal plane. The shape of the end plate is mostly oblong at L3 IEP(59%), equally distributed between oblong and eccentric at L4 SEP (o=43.5%, e=46.5%), eccentric at L4 IEP (e=62.5%), eccentric at L5 SEP (e = 59.0%), eccentric at L5 IEP (e=94.0%), and flat at S1 SEP (f=82.5%). As there is a difference in the shape of the endplate at each level and they are not uniform, there is a need to focus on the sagittal shape of the footplate to avoid subsidence and mismatch of the footplate in cases of endplate concavity

To assess the clinical and radiologic outcome of MM patients with thoracic spine involvement and concomitant pathologic sternal fractures with a resultant severe sagittal plane deformity. A prospective cohort study (n=391) was performed over a 7-year period at a national tertiary referral centre for the management of multiple myeloma with spinal involvement. Clinical, serological and pathologic variables, radiologic findings, treatment strategies and outcome measures were prospectively collected. Pre-treatment and post-treatment clinical outcome measures utilised included EQ-5D, VAS, ODI and RMD scoring systems. 13 MM patients presented with a severe symptomatic progressive sagittal plane deformity with a history of pathologic thoracic compression fractures and concomitant pathologic sternal fracture. All patients with concomitant sternal fractures displayed the radiographic features and spinopelvic parameters of positive sagittal malalignment and attempted clinical compensation. All patients had poor health related quality of life measures when assessed. Pathologic sternal fracture in a MM patient with thoracic compression fractures is a risk factor for the development of a severe thoracic kyphotic deformity and sagittal malalignment. This has been demonstrated to be associated with a very poor health related quality of life

Background: The Oxford unicompartmental knee replacement (UKR) use in the lateral compartment has been associated with a reduced flexion range and diminished femoral rollback. It is postulated that this may be due to a flat tibial tray replacing the domed anatomy of the lateral tibia, tightening the posterolateral flex-ion gap. A new design incorporating a domed tibial component and a biconcave meniscal bearing has been developed to increase; (i) the posterolateral flexion gap in deep knee flexion (ii) meniscal bearing movement and (iii) lateral femoral condyle (LFC) rollback. A cadaveric study was designed to test these three outcomes. Methods: The sagittal plane kinematics of seven thawed fresh frozen cadaver specimens within an upright Oxford testing rig were assessed under three different conditions; (i) intact normal cadaver knee (ii) flat lateral Oxford UKR (iii) domed lateral Oxford UKR. Each condition was tested during three ranges of motion (ROM) and data recorded during a flexion or extension half cycle. Knee flexion angle (KFA) and displacement measures of the lateral collateral ligament (LCL), LFC rollback and anteroposterior meniscal bearing movement were performed throughout knee ROM using four [3 linear, 1 rotary] potentiometer devices. Potentiometer data was recorded as a voltage reading and subsequently converted to either a millimetre displacement or degree measure using a calibration formula. All data points were compared at 10 degree interpolations of KFA. Results: The flexion half cycles demonstrated the flat Oxford lateral UKR achieved 80.7% of normal cadaveric LFC rollback. The domed Oxford lateral UKR achieved 108.8% of normal cadaveric LFC rollback. The ratio of LFC rollback in the domed to flat UKR’s was 1.35 times (134.9%). Meniscal bearing movement in flexion demonstrated a domed to flat UKR ratio of 1.3 times (129.7%). Similar values were obtained for extension half cycles in favour of the domed Oxford lateral UKR. No significant differences were identified in LCL measures. Conclusions: The domed Oxford lateral UKR implant allows for improved bearing movement and femoral rollback when compared to the flat Oxford lateral UKR. The sagittal plane kinematics of the domed Oxford lateral UKR as represented by femoral rollback values approximate those of the normal cadaver knee

Précis: Gravity Line (GL) measurement by forceplate offers key information on standing balance. In this study x-ray measurements and GL offsets were calculated in two adult: volunteer controls, sagittal plane deformity patients. The deformity group revealed significant pelvic retroversion and posterior sacral displacement regarding GL and heels. However, GL-heel and GL-femoral head offsets were similar indicating that sagittal plane deformity may induce posterior pelvic translation and retroversion in order to maintain an inherent ideal/fixed GL-heel relationship. Introduction: Sagittal spinal imbalance in the adult remains poorly understood and challenging. Limitations of radiographic analysis have lead researchers to apply forceplate technology to enhance the study of spinal balance through evaluation of the gravity line (GL). The aim of this study was to investigate differences between asymptomatic adults and patients with sagittal spinal deformities, with a hypothesis that imbalance would lead to changes in the GL – spinal relationship. Material and Method: This prospective study included 44 asymptomatic subjects (mean 57yo) and 40 patients with sagittal deformities (mean 65yo, inclusion criteria: L1-S1 lordosis< 258, Pelvic Tilt> 208, C7 plumbline> 5 cm). Coronal plane deformities were excluded. Full-length free-standing sagittal radiographs were obtained with simultaneous acquisition of the GL and heel position (by forceplate). Spino-pelvic radiographic parameters were calculated and distances (offsets) from the GL analysed. Group differences were evaluated by independent sample t-tests. Results: Groups did not differ in age, thoracic kyphosis, offsets from femoral heads to heels, femoral heads to GL, and GL to heels. As per inclusion criteria the sagittal deformity group had greater mean C7 plumbline (8cm vs 0cm), increased pelvic tilt (27° vs 13°) and loss of lordosis (46° vs 58°). The sagittal deformity group also had greater pelvic incidence (60° vs 51°), anterior trunk inclination (−3° vs −11°), S1 displacement toward the heels (distance decreased, 87 vs. 46mm). All differences p< 0.001. Discussion: The sagittal spinal deformity group revealed marked differences; the sacrum has a more posterior position in relation to the GL and heels. However, the GL to femoral head offset was not markedly influenced. The additional finding of no change in the GL to heel offset and rather fixed GL-femoral head offset appears to indicate that sagittal spinal deformity induces a posterior sacral translation and pelvic retroversion in order to maintain a fixed GL-heel relationship

Previous studies of osteoarthritic knees have examined the relationship between the variables body mass index (BMI) and weight on the one hand and coronal plane deformity on the other. There is a consensus that weight and BMI are positively correlated to the degree and progression of a varus deformity. However, there does not appear to be a consensus on the effect of these variables on knees with a valgus deformity. Indeed, the view has been expressed that in knees with a severe deformity a relationship might not exist. A review of these studies reveals that in all cases, the alignment of the lower limb was obtained from a standing antero-posterior long leg radiograph. In no cases was the deformity in the sagittal plane measured. This study analyses the relationship between BMI, weight, deformity in the sagittal plane and valgus deformity. The study group consisted of 73 patients with osteoarthritis and valgus knees. All of them had failed conservative treatment for their symptoms and were listed for navigated TKA. Their weight and height were measured two weeks preoperatively and the BMI calculated. At operation the coronal and sagittal deformities were measured using the Orthopilot. ®. navigation system (BBraun Aesculap, Tuttlingen). The results were analysed using SPSS 15. Regression analysis showed a significant relationship (p< 0.05) with a negative correlation between valgus deformity and weight. the correlation coefficient for flexed knees (−0.59) showed a moderately strong relationship whereas that for extended knees (−0.38) showed a relatively weak relationship. It is acknowledged that there is an increased force on the lateral compartment with increased valgus deformity. a larger deformity causes a larger moment arm about the centre of the knee. this study has shown that at the time of surgery, individuals with lower weights have larger valgus deformities. we postulate, therefore, that when the moment due to the weight of the individual and the length of the moment arm exceeds a certain value, a symptomatic threshold is crossed. in the presence of a fixed flexion deformity, the force on the patella-femoral joint is increased, contributing further to the onset of discomfort. Further investigation into the subsets of valgus knees appears to be warranted

Introduction and purpose: Pelvic tilt (PT) on the sagittal plane when standing can be defined as the rotation of the pelvis on a transverse axis. The use of PT is indicated for patients with chronic lumbar pain and/or spondylolisthesis. Current IP measurement methods require the use of radiographs or very complicated equipment. The purpose of this study is to describe a new fast and easy-to-use IP measurement technique and analyze its validity and reproducibility. Materials and methods: The measurement system consists in calculating the height of the anterosuperior and posterosuperior iliac spines (to the ground) and the distance between them. Then, by means of a mathematical formula, a determination is made of the inclination of the plane that runs through the four spines with respect to the horizontal. Reproducibility was analyzed through repeat measurements of a group of 12 healthy volunteers. The validity of the method was analyzed by comparing the measurements obtained with those made on the basis of the lateral pelvis radiographs of 30 volunteers. Results: The system described can be used to calculate the value of IP fast and with no need of radiographs or complicated equipment. The intraclass interobserver correlation coefficient measured for the method was .90 and the interobserver correlation coefficient was .80, which were considered excellent results. The mean errors observed when comparing the values obtained with the radiograph measurements were of less than 2° (R2: .48) (significant p< 0.001). Conclusions: The measurement method described is easy to use, reproducible and valid vis-á-vis the use of radiographs

The final alignment of Patient Specific Instrumentation (PSI) TKA relies on the accuracy and the correct placement of the 3-D moulds, precision of saw cuts, soft tissue balancing and cementing technique. We aimed to compare the predicted alignment between PSI and Articulated Surface Mounted (ASM) computer navigation. Eight consecutive patients underwent knee replacement using MRI based PSI (Zimmer) with planning of 0º femoral and tibial mechanical alignment. After placing the conventional cutting blocks over the pins (placed according to PSI), the predicted alignment of cuts was verified with ASM navigation. PSI technique was used regardless of navigation values and alignment was compared. Good correlation was found for tibial cuts (maximum variation: coronal plane – 1º, sagittal plane – 2º) and femoral cuts in the sagittal plane (maximum variation 2º). However, in two patients the coronal plane variation in femur was > 2º (3º and 4º respectively). Navigation predicted combined final alignment of 5º valgus and 4º valgus in these patients. However, long leg standing x-rays revealed neutral and 1º valgus alignment in those two patients respectively, matching closely with PSI prediction. Final alignment in long-leg standing x-rays were independently reported by a musculoskeletal radiologist. Six knees were in neutral mechanical alignment (including the 2 navigation predicted outliers). The remaining 2 knees had a maximum deviation of 2 degrees from neutral. We conclude that there was overall good correlation between PSI and navigation. Even in cases where navigation predicted more than 3º combined varus/valgus alignment, PSI prediction was more accurate on long leg views