Abstract. Aims. Vertebral body tethering (VBT) is a non-fusion technique to correct scoliosis allowing correction of scoliosis through growth modulation (GM) by tethering the
This study aimed to describe the morphology of the coracoid process and determine the frequency of commonly observed patterns. The second purpose was to determine the location of inferior tunnel exit with superior based tunnel drilling and the superior tunnel exit with inferior based tunnel drilling. A sample of 100 dry scapulae for the morphology aspect and 52 cadaveric embalmed shoulders for tunnel drilling were used. The coracoid process was described qualitatively and categorized into 6 different shapes. A transcoracoid tunnel was drilled at the centre of the base. Twenty-six shoulders were used for the superior-inferior tunnel drilling approach and 26 for the inferior-superior tunnel drilling approach. The distances to the margins of the coracoid process, from both the entry and exit points of the tunnel, were measured. Eight coracoid processes were of
Tibial plateau fracture reduction involves restoration of alignment and articular congruity. Restorations of sagittal alignment (tibial slope) of medial and lateral condyles of the tibial plateau are independent of each other in the fracture setting. Limited independent assessment of medial and lateral tibial plateau sagittal alignment has been performed to date. Our objective was to characterize medial and lateral tibial slopes using fluoroscopy and to correlate X-ray and CT findings. Phase One: Eight cadaveric knees were mounted in extension. C-arm fluoroscopy was used to acquire an AP image and the C-arm was adjusted in the sagittal plane from 15° of cephalad tilt to 15 ° of caudad tilt with images captured at 0.5° increments. The “perfect AP” angle, defined as the angle that most accurately profiled the articular surface, was determined for medial and lateral condyles of each tibia by five surgeons. Given that it was agreed across surgeons that more than one angle provided an adequate profile of each compartment, a range of AP angles corresponding to adequate images was recorded. Phase Two: Perfect AP angles from Phase One were projected onto sagittal CT images in Horos software in the mid-medial compartment and mid-lateral compartment to determine the precise tangent subchondral anatomic structures seen on CT to serve as dominant bony landmarks in a protocol generated for calculating medial and lateral tibial slopes on CT. Phase Three: 46 additional cadaveric knees were imaged with CT. Tibial slopes were determined in all 54 specimens. Phase One: Based on the perfect AP angle on X-ray, the mean medial slope was 4.2°+/-2.6° posterior and mean lateral slope was 5.0°+/-3.8° posterior in eight knees. A range of AP angles was noted to adequately profile each compartment in all specimens and was noted to be wider in the lateral (3.9°+/-3.8°) than medial compartment (1.8°+/-0.7° p=0.002). Phase Two: In plateaus with a concave shape, the perfect AP angle on X-ray corresponded with a line between the superiormost edges of the anterior and posterior lips of the plateau on CT. In plateaus with a flat or
Introduction. 3D printed Patient Specific Guides (PSGs) can improve the accuracy of joint-replacement. Pre-operative CT bone models are used to design a PSG that fits the patient's specific bone geometry. A key design requirement is to maximize docking robustness such that the PSG can maintain a stable position in the planned location. However, current PSG designs are typically manually defined, lack a quantitative assessment of robustness, and have an unknown consistency of docking rigidity between patients. Limited research exists on the stability and robustness of surgical guides, and no software packages are available to facilitate this analysis. Our goal was to develop such a software. Methods. In this paper, the contact between a patient's bone and the PSG is modelled using robotic grasping theory, and its docking robustness is quantified by analysis of the PSG's grasp wrench space (GWS) (i.e. the combination of contact forces and torques between the bone and PSG). To this end, a PSG design and analysis tool with a graphical user interface was developed in MATLAB. This tool allows the user to load shapes (e.g. STL bone models), select and manipulate possible contact points, and optimize the contact point locations according to the largest-minimum resisted wrench (LRW) that the grasp can resist in any direction. The LRW is a grasp quality metric equivalent to the radius of the largest (hyper)sphere contained within the
INTRODUCTION. In native knees anterior cruciate ligament (ACL) and asymmetric shape of the tibial articular surface with a
INTRODUCTION. ACL retaining (BCR) Total Knee Arthroplasty (TKA) provides more normal kinematics than ACL sacrificing (CR) TKA. However, in the native knee the ACL and the asymmetric shape of the tibial articular surface with a
The extent of soft-tissue release and the exact structures that need to be released to correct deformity and balance the knee has been a controversial subject in primary total knee arthroplasty. Asian patients often present late and consequently may have profound deformities due to significant bone loss and contractures on the concave side, and stretching of the collateral ligament on the
Dorr bone type is both a qualitative and quantitative classification. Qualitatively on x-rays the cortical thickness determines the ABC type. The cortical thickness is best judged on a lateral x-ray and the focus is on the posterior cortex. In Type A bone it is a thick
The evolution of operative technology has allowed correction of complex spinal deformities. Neurological deficits following spinal instrumentation is a devastating complication and the risk is especially high in those with complex sagittal and coronal plane deformities. Prior to intraoperative evoked potential monitoring, spinal cord function was tested using the Stagnara Wake up test, typically performed after instrumentation once the desired correction has been achieved. This test is limited as it does not reflect the timeframe in which the problem occurred and it may be dangerous to some patients. Intraoperative neuromonitoring allows timely feedback of the effect of instrumentation and curve correction on the spinal cord. Pedicle screws that are malpositioned can result in poor fixation or neuronal injury. Evoked EMG monitoring can aid in accurate placement. A positive EMG response can alert the surgeon to a potential pedicle breech and allow them to reassess the placement of their hardware intraoperatively. The stimulation threshold is affected by the amount of surrounding bone acting as an insulator to electrical conduction and is variable in different regions of the spine. In the non-deformed, lumbar spine stimulation thresholds have been established. Such guidelines have not been well-developed for the thoracic spine, or for severely scoliotic spines. Thus our primary objective was to compare the stimulation threshold of the apical pedicle on the concave side to the stimulation threshold of the pedicles at the upper and lower instrumented levels. Intraoperative EMG stimulation thresholds were done at 192 apical pedicles on the concave side of the deformity and then compared to those thresholds found at 169 terminal level pedicles. Only pedicles for which a stimulation threshold was found were reported and excluded those where a breech was suspected. The lowest stimulation required for an EMG response was documented to a maximum stimulation of 20 mA. The mean threshold at the apex was 16.62 milliamps (mA) compared to 18.25mA at the terminal levels. This was compared with the t-test and showed a statistically significant difference (p<0.05). In this study we report only the thresholds for the concave side, the pedicle that is most likely to be reduced in size. The threshold for stimulation is reduced compared to those seen at the highest and lowest instrumented level. Most of the apexes are located in the mid-thoracic spine with the highest instrumented levels being in the high thoracic spine and the lowest levels being in the lumbar spine. This study provides preliminary evidence that the apical, concave pedicle has a lower threshold than the end pedicles and one cannot rely on established thresholds from different areas of the spine. The surgeon should be cognisant of these differences when instrumenting at the apical level. Ongoing work is examining the
Total knee arthroplasty (TKA) is widely accepted as a successful treatment option for the pain and limitation of function associated with severe joint disease. The ideal knee arthroplasty implant should provide reliable pain relief and normal levels of functional strength and range of motion. However, there are still a number of implant-specific problems following knee arthroplasty, such as irregular kinematics, polyethylene wear and poor range of motion. MRI and cadaveric studies have highlighted important kinematics during movement of the native knee. In particular, flexion of the joint results in a phenomenon referred to as “roll back and slide”. This essentially describes posterior translation of the femur on the tibia which in turn has a two-fold biomechanical function: to increase the lever arm of the quadriceps and allow clearance of the femur from the tibia in deep flexion. During extension of the joint, the femur rolls forward increasing the lever arm of the hamstrings to act as a brake on hyperextension. Additional rotation of the joint arises in the axial plane. This is attributed to the concave tibial plateau and relatively fixed meniscus on the medial compartment of the joint in comparison to a lateral
Introduction. The longevity of highly cross-linked polyethylene (XLPE) bearings is primarily determined by its resistance to long-term oxidative degradation. Addition of vitamin E to XLPE is designed to extend in vivo life, although it has unintended consequences of inducing higher frictional torque and increased wear when articulating against metallic femoral heads. 1–3. Conversely, lower friction was observed when oxide ceramic heads were utilized. 3. Previous studies suggest that oxide ceramics may contribute to XLPE oxidation, whereas a non-oxide ceramic, silicon nitride (Si. 3. N. 4. ), might limit XLPE's degradation. 4. To corroborate this observation, an accelerated hydrothermal ageing experiment was conducted using static hydrothermal contact between XLPE and commercially-available ceramic femoral heads. Materials and Methods. Two sets of four types of ceramic femoral heads, consisting of three oxides (Al. 2. O. 3. BIOLOX. ®. forte, and ZTA BIOLOX. ®. delta, CeramTec, GmbH, Plochingen, Germany; and m-ZrO. 2. OXINIUM. TM. , Smith & Nephew, Memphis, TN, USA) and one non-oxide (MC. 2®. Si. 3. N. 4. , Amedica Corp., Salt Lake City, UT, USA) were cut into hemispherical sections. Six highly crosslinked polyethylene liners (X3. TM. Stryker Orthopedics, Inc., Mahwah, New Jersey, USA) were also sectioned, gamma irradiated (32 kGy), and mechanically clamped (25 kN) to the
Background. Reverse Geometry shoulder replacement requires fixation of a base plate (called a metaglene) to the glenoid to which a
The Oxford unicompartmental knee replacement (UKR) was introduced in 1976 with good results. Mobile bearings in the lateral compartment have been associated with unacceptably high bearing dislocation rates, due to greater movement between the lateral femoral condyle and tibia, and the lateral collateral ligament's laxity in flexion. The new domed implant is designed to counter this with a
A retrospective descriptive preliminary study on early experience using all pedicle screw correction. Pedicle screw fixation enables enhanced correction of spinal deformities. However, the technique is still in early development in our clinic. Tends of the scoliosis patient to come in late ages make maximum correction failed. A total 16 patients are subjected to pedicle screw fixation for spinal deformities were analyzed descriptively as an early follow-up in the last two-year. 14 patients are girl and 2 are boys. The age range between 12 to 18 year. 8 are Kings type II and 8 are Kings type III, 212 screws were inserted between Th3 – L2 (14-18 screws per-patient), all concave pedicles were inserted with screws but in
Introduction. Peroneal tendon subluxation & dislocation is a rare phenomenon. It is a commonly misdiagnosed cause of lateral ankle pain and instability. Aim(s). Our aim was to establish the morphometric (quantification of components) features of retromalleolar fibular groove in cadavers using 3D technique. Study points. To map the version and inclination based on the 3D techniques. To determine the depth of peroneal groove sufficient to prevent subluxation of tendons. Method/materials. We used 12 of embalmed lower extremities. 6 males and 6 females. All were Caucasians (Age: 61–94). The orientation is calculated using the cartilage boundary of the peroneal groove and using the centroid of the curved surface of the groove. We used rhinoceros software for data collection and mapping of peroneal grooves using 3D imaging Microscribe Digitiser. Results. The retromalleolar groove was concave in 8 ankles. Flat in 3 (female 50%) and
Introduction:. Large diameter femoral heads have been used successfully to prevent dislocation after Total Hip Arthroplasty (THA). However, recent studies show that the peripheral region of contemporary femoral heads can directly impinge against the native soft-tissues, particularly the iliopsoas, leading to activity limiting anterior hip pain. This is because the spherical articular surface of contemporary prosthesis overhangs beyond that of the native anatomy (Fig. 1). The goal of this research was to develop an anatomically shaped, soft-tissue friendly large diameter femoral head that retains the benefits of contemporary implants. Methods:. Various Anatomically Contoured femoral Head (ACH) designs were constructed, wherein the articular surface extending from the pole to a theta (θ) angle, matched that of contemporary implants (Fig. 2). However, the articular surface in the peripheral region was moved inward towards the femoral head center, thereby reducing material that could impinge on the soft-tissues (Fig. 1 and Fig. 2). Finite element analysis was used to determine the femoroacetabular contact area under peak in vivo loads during different activities. Dynamic simulations were used to determine jump distance prior to posterior dislocation under different dislocation modes. Published data was used to compare the implant articular geometry to native anatomy (Fig. 3). These analyses were used to optimize the soft-tissue relief, while retaining the load bearing contact area, and the dislocation resistance of conventional implants. Results:. The resulting ACH prosthesis retained the large diameter profile of contemporary implants over an approximately hemispherical portion (Fig. 2). Beyond this, the peripheral articular surface was composed of smaller
Introduction:. While kinematic abnormalities of contemporary TKA implants have been well established, a solution has not yet been achieved. We hypothesized that contemporary TKA implants are not compatible with normal soft-tissue function and normal knee motion. We propose a novel technique for reverse engineering advanced implant articular surfaces (biomimetic surface), by using accurate 3D kinematics of normal knees. This technique accounts for surgical placement of the implants, and allows design of tibial and femoral articular surfaces in conjunction. Methods:. Magnetic resonance imaging was used to create 3D knee models of 40 normal subjects (24 male, 16 female, age 29.9 ± 9.7 years), and bi-planar fluoroscopy was used to capture 3D knee motion during a deep knee bend. These data were combined to create a 3D virtual representation of an average normal knee and its motion pathway. A TKA femoral component was mounted on the average knee, and moved through its normal kinematic pathway to carve out an articular surface from a tibial template (Fig. 1 and 2). The geometry of the resulting biomimetic tibia was compared to that of the native tibia, and a contemporary TKA tibial insert that uses the same femoral component. Results:. The biomimetic tibia had a dished medial plateau and a
Introduction:. Dual Mobility (DM) hip implants have gained popularity for the treatment and preventions of instability. In DM implants a large diameter mobile insert matches the native femoral head size. However, studies have shown that the peripheral regions of such large diameter implants overhang beyond the native anatomy and can directly impinge against nearby soft tissues, especially the iliopsoas, leading to groin pain (Fig. 1). Soft-tissue impingement can also trap the mobile DM insert, leading to damage of its peripheral rim, which secures the small diameter inner head (Fig. 2). The goal of this research was to develop an anatomically contoured soft-tissue friendly DM insert. Methods:. Various Anatomically Contoured Dual Mobility (ACDM) insert designs were constructed, wherein the outer articular surface extending from the pole to a theta (θ) angle, matched that of contemporary implants (Fig. 3). However, the articular surface in the peripheral region was moved inward towards the center, thereby reducing implant volume that could impinge on the soft tissue (Fig. 1 and Fig. 3). Finite element analyses were used to determine the insert-acetabular contact area under peak in vivo loads during different activities. Finite element analysis was also used to determine resistance to extraction of the inner head. Published data was used to compare the implant articular geometry to native anatomy. These analyses were used optimize the soft-tissue relief, while matching the load bearing contact area and the resistance to extraction of the inner head in contemporary implants. Results:. The resultant ACDM insert had the outer profile of contemporary implants over approximately a hemispherical portion (Fig. 3). Beyond this, the peripheral articular surface was composed of smaller
Introduction. After total knee arthroplasty (TKA) with a PCL-retaining implant the location of the tibiofemoral contact point should be restored in order to obtain normal kinematics. The difficulty during surgery is to control this location since the position of the femur on the tibia cannot easily be measured from the back of the joint. Therefore, we developed a simple “spacer technique” to check the contact point indirectly in 90° flexion after all bone cuts are made by measuring the step-off between the distal cut of the femur and the anterior edge of the tibia with a spacer in place. The goal of this experiment was to investigate whether this new PCL balancing approach with the spacer technique created the correct contact point location. Methods. Nine fresh-frozen full leg cadaver specimens were used. After native testing, prototype components of a new PCL-retaining implant were implanted using navigation and a bone-referenced technique. After finishing the bone cuts of tibia and femur, the spacer was inserted in flexion and positioned on the anterior edge of the bony surface to measure the step-off. If necessary, an extra cut was made to balance the PCL. The specimen was mounted on the knee kinematics rig and a squat with constant vertical ankle force (130N) and constant medial and lateral hamstrings forces (50N) was performed between 30° and 130° of knee flexion. The trajectories of the reflective tibial and femoral markers were continuously recorded using six infrared cameras. The projections of the femoral condylar centers on the horizontal plane of the tibia were calculated and compared. Results. Of the 9 specimens, the calculated step-off was correct in 7 after finishing the bone cuts and in 2 specimens an additional tibia cut with 2–3 degrees more slope was sufficient to achieve the correct step-off. No lift-off of the tibial tray occurred during the tests. The patterns of the kinematics of the native and replaced knee showed a considerable similarity (fig 1). The projected medial femoral condylar center of the knee implant is at the same position as the projected medial femoral condylar center of the native knee. No paradoxical roll forward is seen in the knee implants, showing that the PCL balancing apparently seems to work quite well. The projected lateral femoral condylar center of the knee has a similar kinematic pattern in flexion before and after TKA. The knee implant shows a slightly more anterior location near extension but this is only marginal. Discussion and conclusion. The kinematics of the PCL-retaining implant are on average comparable to the kinematic pattern of the native knee. Apparently, the joint surfaces of the anatomic knee designed with a dished medial insert surface and a
Introduction. Despite the theoretical advantages of mobile bearings for lateral unicompartmental knee replacement (UKR), the failure rate in the initial published series of the lateral Oxford UKR's was unacceptably high. The main cause of failure was early dislocation. In contrast, dislocations of bearings in medial UKR's are rare. The lateral compartment present a higher laxity in flexion than the medial. An adaptation of the lateral design by introducing a
