Genu recurvatum deformity is uncommon in arthritic knees undergoing total knee arthroplasty (TKA). We retrospectively analysed radiographs and navigation data to determine the clinical and radiographic results of computer-assisted TKA in knee arthritis with recurvatum deformity. Based on alignment data obtained during computer assisted (CAS) TKA, 40 arthritic knees (36 patients) with a recurvatum deformity of at least 5° were identified. The mean recurvatum deformity was 8.7° (6° to 14°). On preoperative standing hip-ankle radiographs, 23 limbs (57.5%) had a mean varus deformity of 169.4° (153° to 178°) and 17 limbs had a mean valgus deformity of 189.2° (182° to 224°). The intraoperative navigation data showed mean tibial resection of 7.5mm (4.6 to 13.4mm) and distal femur resection of 7.5mm (3.3 to 13mm) with a mean final extension gap of 21.2mm and a flexion gap at 90° of 21.1mm and on extension. On table, the mean knee deformity in sagittal plane was 3° flexion (1.5° to 4.5° flexion). Postoperatively, the mean HKA angle on standing hip-ankle radiographs was 179.2° (177° to 182°). On postoperative lateral radiographs, joint line in extension was moved distally in 35 limbs by 2.3mm (0.3 to 4mm) and proximally in 5 limbs by 2.2mm (2.2 to 2.4mm); the mean preoperative posterior femoral offset of 28.7 mm changed to 27.9 mm postoperatively. At a mean follow up 28 months (14- 48 months) the knee, function, and pain scores improved by 61, 48, and 28 points, respectively and there was no recurrence of recurvatum deformity at final follow up. Genu recurvatum is a notoriously difficult condition to address at TKA. The challenges are to be able to detect it at surgery and take appropriate measures in terms of resection and releases to correct it satisfactorily. Computer assisted TKA helps to achieve excellent deformity correction, limb alignment, gap balancing and function in patients with recurvatum deformity by accurately quantifying and helping to modify the amount of bone cuts and titrate soft tissue release

Introduction. Genu recurvatum is a deformity rarely seen in patients receiving total knee arthroplasty. This deformity is defined as hyperextension of the knee greater than 5°. The incidence of recurvatum has been cited in the literature as less than 1%. Purpose. The purpose of this study was to report data on 1510 consecutive total knee replacements (TKR) with navigation to demonstrate that the incidence of genu recurvatum is higher than what is cited in the literature. Methods. This is a retrospective review that was approved by our health science institutional review board. We reviewed resting, intra-operative alignment of 206 navigated total knee arthroplasty cases with recurvatum. This is data from 4 surgeons who are lower extremity joint replacement physicians. The range of motion (ROM) is measured and recorded by the attending physician during routine physical examination of the lower extremity. Demographic data was used to describe the patient group. The data will include pre-operative, intra-operative and post-operative ROM. The intra-operative data will be captured by the navigation system, this sytem is accurate to 1° and 1mm. The post-operative ROM will be obtained from an office visit. We are interested in the post-operative ROM to demonstrate correction of the recurvatum. Results. One thousand five hundred and ten primary TKR were reviewed for this study. Two hundred and six patients (13.6%) had genu recurvatum as measured by the navigation computer. The range of recurvatum was 0.5–30°; mean 5 degrees (STD 4.3°). Sixty six patients had >5 degrees of recurvatum (4.4%). Only 2 patients had recurvatum recorded on their pre-operative office visit. These 2 patients did not have extreme recurvatum, 3° and a few degrees on walking respectively. No patient had recurvatum at the 4 year visit (visit range 3 months – to 4 years). The primary diagnosis for the group was osteoarthritis, 92 %. All cases of recurvatum were treated with under resection of the femur and correction of the coronal plane. All cases were corrected intraoperatively. Conclusion. Etiology of recurvatum can be due to bony insufficiency at the anterior tibia, insufficiency at both femoral condyles or laxity of the posterior capsule and ligaments. During surgery this can be addressed by under resection of the femur and undersizing the femoral component to increase the flex space, or soft tissue tightening can be implemented. Our surgical technique aimed to balance hyperextension with reduction of the distal femoral cut. Coronal balance is also important in the management of hyperextension. Current total knee designs lack the extension cam effect and make sagital balancing critical. Recurvatum is difficult to correct after total knee arthroplasty and this issue is important to address at the time of primary surgery. The use of a navigation system helped us appreciate a deformity that is not easily detected during routine examination. This study found that genu recurvatum in patients receiving TKR is significantly higher than what is reported in the literature. This finding has important implications for the management of a small percentage but nonetheless significant number of patients. This deformity is not appreciated in the clinical setting during routine examination

There is a difference between “functional instability” of a total knee arthroplasty (TKA) and a case of “TKA instability”. For example a TKA with a peri-prosthetic fracture is unstable, but would not be considered a “case of instability”. The concept of “stability” for a TKA means that the reconstructed joint can maintain its structure and permit normal motion and activities under physiologic loads. The relationship between stability and alignment is that stability maintains alignment. Instability means that there are numerous alignments and almost always the worst one for the loading condition. In the native knee, “instability” is synonymous with ligament injury. If this were true in TKA, then it would be reasonable to treat every “unstable TKA” with a constrained implant. But that is NOT the case. If the key to successful revision of a problem TKA is understanding (and correcting) the specific cause of the problem, then deep understanding of why the TKA is unstable is essential. A case of true “instability” then, is the loss of structural integrity under load as the result of problems with soft tissue stabilizing structures and/or the size or position of components. It is rare that ligament injury alone is the sole cause of instability (valgus instability invariably involves valgus alignment; varus instability usually means some varus alignment and compromised lateral soft tissues). There will be forces (structures) that create instability and forces (structures) that stabilise. There are three categories of instability: Varus-valgus or coronal: Assuming that the skeleton, implant and fixation are intact. These are usually cases that involve ligament compromise, but the usual cause is CORONAL ALIGNMENT, and this must be corrected. The ligament problem is best solved with mechanical constraint. Gait disturbances that increase the functional alignment problems (hip abductor lurch causing a valgus moment at the knee, scoliosis) may require attention of additional compensation with re-alignment. Plane of motion: Both fixed flexion contractures and recurvatum may result in buckling. The first by exhaustion of the quadriceps (consider doing quadriceps “lunges” with every step) and the second because recurvatum is usually a compensation for extensor insufficiency. The prototype for understanding recurvatum has always been polio. This is perhaps one of the most difficult types of instability to treat. The glib answer has been a hinged prosthesis with an extensor stop but there are profound mechanical reasons why this is flawed thinking. The patient with recurvatum instability due to neurologic compromise of the extensor should be offered an arthrodesis, which they will likely decline. The simpler problem of recurvatum secondary to a patellectomy will benefit from an allograft reconstruction of the patella using a modified technique. A common occurrence is obesity with patellofemoral pain, that the patient has managed with a “patellar avoidance” or “hyperextension gait”. Plane of motion instability is a problem of the EXTENSOR MECHANISM DEFICIENCY. Flexion instability. This results from a flexion gap that is larger than the extension gap, where a polyethylene insert has been selected that permits full extension but leaves the flexion gap unstable. These patients achieve remarkable flexion easily and early, but have difficulties with pain and instability on stairs, with recurrent (non-bloody) effusions and peri-articular tenderness. Revision surgery is necessary. Flexion instability may also occur with posterior stabilised prostheses. So-called “mid-flexion” instability is a contentious concept, poorly understood and as yet, not a reported cause for revision surgery distinct from “FLEXION INSTABILITY”. Flexion instability is a problem of GAP BALANCE

Introduction. Genu recurvatum deformities are unusual before total knee arthroplasty (TKA), occurring in less than 1% of patients. The purpose of this study is to evaluate the clinical and radiographic results of primary TKA in patients that had recurvatum deformities before surgery. Patients and Methods. The inclusion criteria was to have recurvatum deformity over 10 degrees on lateral standing X-ray view. We retrospectively reviewed 22 knees with pre-operative recurvatum deformities, and the incident was 1.0% of all TKAs at our hospital. The etiology of the arthritis was osteoarthritis in 21 knees, of which 3 knees were neuropathic disease, and rheumatoid arthritis in 1 knee. There were 6 men and 16 women, and the average age was 73.3 years (range, 53 to 83 years) at the time of operation. The average follow-up period was 15 months (range, 3 to 81 months). We performed to use medial parapatellar approach and bone cutting was done by measured resection technique. The surgical knacks were resection of less distal femur and proximal tibia bone to make extension gap tightly, additionally decrease the tibial posterior slope. Posterior-stabilizer (PS) implants (NexGen LPS: Zimmer, Bisurface KU4+: JMM) were used in 20 knees and constrained implants (NexGen RH knee: Zimmer, Endo-Model Hinge Knee: Link) were in 2 knees with neuropathic joints. Results. The averaged Knee Society Knee and Function score improved from 33.1 points to 94.1 points, and 28.0 points to 60.5 points at the time of the last follow-up. The femorotibial angle changed from averaged 183.4 degrees (range, 162 to 195 degrees) preoperatively to averaged 173.3 degrees (range, 170 to 177 degrees). Preoperative hyperextension was averaged 18.2 degrees (range, 10 to 40 degrees). Intraoperatively, the hyperextension deformity was corrected in all cases. The tibial posterior slope was averaged 1.7 degrees (range, −2.7 to 6 degrees). The final hyperextension improved averaged 6.9 degrees (range, −1.7 to 26.6 degrees), all but one knee were corrected. One case treated with a standard PS type, who was associated with neuropathic disease, had a recurrence of recurvatum deformity and required revision surgery. Discussion. Recurvatum may be associated with a severe osseous deformity, capsular or ligamentous laxity, and neuromuscular disease. Surgical solutions may be to use a standard PS prosthesis with a slight underresection of the bone edge, and decrease tibial posterior slope. An alternative solution is to use a rotating-hinge prosthesis with less than antigravity quadriceps strength for neuromuscular disease

Introduction. The assessment of leg length is essential for planning the correction of deformities and for the compensation of length discrepancy, especially after hip or knee arthroplasty. CT scan measures the “anatomical” lengths but does not evaluate the “functional” length experienced by the patients in standing position. Functional length integrates frontal orientation, flexion or hyperextension. EOS system provides simultaneously AP and lateral measures in standing position and thus provides anatomical and functional evaluations of the lower limb lengths. The objective of this study was to measure 2D and 3D anatomical and functional lengths, to verify whether these measures are different and to evaluate the parameters significantly influencing these potential differences. Material and Methods. 70 patients without previous surgery of the lower limbs (140 lower extremities) were evaluated on EOS images obtained in bipodal standing position according to a previously described protocol. We used the following definitions:. anatomical femoral length between the center of the femoral head (A) and center of the trochlea (B). anatomical tibial length between the center tibial spine (intercondylar eminence) (C) and the center of the ankle joint (D). functional length is AD. global anatomical length is AB + CD. Other parameters measured are HKA, HKS, femoral and tibial mechanical angles (FMA, TMA), angles of flexion or hyperextension of the knee, femoral and tibial torsion, femoro-tibial torsion in the knee, and cumulative torsional index (CTI). All 2D et3D measures were evaluated and compared for their repeatability. Results. Regarding repeatability, an ICC> 0.95 was found for all measurements except for the tibial mechanical angle (0.91 for 2D, 3D 0.92 for 3D). We observed 54/140 lower limbs with Flessum/Recurvatum angles (FRA) >10°. 2D results (mean, SD) were. 41,8mm(2,9) for femoral anatomical length. 36,1mm(2,8) for tibial anatomical length. 78,0mm(5,4) for global anatomical length. 78,5 mm(5,5) for functional length. 7,4°(12,0) for Flessum/Recurvatum angle. −1,5°(6,4) for HKA. 4,9°(2,0) for HKS. 92,1°(3,4) for FMA. 87,1°(3,4) for TMA. 3D results (mean, SD) were. 42,4mm (2,8) for femoral anatomical length. 36,6mm (2,8) for tibial anatomical length. 79,0mm (5,4) for global anatomical length. 78,9mm (5,5) for functional length. 7,2°(12,0) for Flessum/Recurvatum angle. −1,0°(5,9) for HKA. 4,9°(1,5) for HKS. 92,7°(2,7) for FMA. 87,9°(3,9) for TMA. The 2D/3D measurements of functional lengths were statistically significant (p <0.0001. Student's test). For anatomical lengths. 2D/3D measurements were also statistically significant (p <0.0001. Student's test for femoral tibial and global anatomical lengths). Some parameters significantly influenced 2D/3D differences:. for the global anatomical length: FRA P<0,0001, TMA P=0,0173, HKA P=0,0259 and femoro-tibial torsion P=0,0026. for the functional length FRA P=0,0065. Discussion and conclusion. EOS imaging allows to accurately assess the anatomical and functional length experienced by the patient. These new data open new perspectives for planning length or axis corrections and for an optimized evaluation in some medico legal issues after joint replacement or posttraumatic sequelae. This study points out the importance of 3D measurements in outliers cases (varus or valgus cases, flessum or recurvatum of the knee)

Introduction. To report our early experience and suitability over unicortical fixation system to reduce and hold the bone fragments in position during a CHAOS procedure of the femur or tibia during lower limb reconstruction surgery. Materials and Methods. We report a case series of the first consecutive 10 patients (11 bones) for which this CHAOS technique was used between May 2017 and October 2019 by the same surgeon. The novel aspect of the procedure was the use of a unicortical device, Galaxy UNYCO (Orthofix, Verona, Italy), which eliminate the need for any change of fixation during the procedure. It also means the intramedullary canal was left free for the intramedullary nailing. Results. We treated 4 femurs and 7 tibias with this technique without any loss or failure of the construct. We treated uniplanar and multiplanar deformities with the angulations between 8 degrees of valgus to 15 degrees of varus and from 0 to 8 mm translation in the AP view, from 20 degrees procurvatum to 15 degrees recurvatum and 0 to 2 mm translation on the lateral view and from 20 degrees internal rotation to 5 degrees external rotation and 0 to 10 mm translation on axial view. Conclusions. The construct was able to deal with the total tension in the system both in the correction phase and the additional stress applied during insertion of a nail such as reaming and impacting the nail to the canal. The potential advantage also included the possibility of intramedullary nailing without interference with the external fixation device

Total knee arthroplasty is well documented to be a very successful operation, proper alignment and soft tissue balancing is important. Computer navigation for TKA has been available for more than 10 years. This paper reviews our outcomes and the lessons learned from CAS. October 1, 2001 we preformed the first clinical case of a navigated TKA in North America. We tracked our early results at with 1 year of follow up of 150 navigated knee cases and compared there data to 50 non- navigated knees. Long standing lower extremity x-rays were measured to determine mechanical alignment. In 2011 we reviewed all cases to date to determine if there were pin site problems. In 2012 we looked at are recurvatum data. Oct 2011 was our 10. th. year using the computer navigation system for TKA. We reviewed what we have learned and assess our outcome data on patients who were at least 9.5 years post surgery. All patients received long standing lower extremity x-rays pre-operatively and at 10 year follow up. Any problems or revisions were noted. Our early results will be compared to our 10 year results. Our 1 year results showed no difference in clinical outcome or range of motion compared to the non-navigated group. The navigated knee group had better alignment; 52% were in neutral alignment, vs. 23% in the non-navigated group. Overall the navigated group, 80% of all alignment was within 1.5 degrees of neutral while the non-navigated groups 80 % of cases were between 5° valgus and 4° varus. Our data for 10 year follow up (range 9.5–10.5 years) is the similar to our early results. We have seen 42 patients, 44 knees. The alignment from long standing lower extremity x-rays, 53% were neutral or +/− 1°. Twenty eight knees of 43 were +/− 3°. There were 3 revisions in this small group. One was revised for a loose tibial base plate with osteolysis on the tibia and femur. The revision was 10 years after the index surgery. There were 2 other revisions, both for infection, were treated with a poly exchange and wash out. To date we have done 2030 navigated knee cases and our data shows that 13.9% demonstrate genu recurvatum. The range was 0.5° to 30°, 104 patients, 5.1% had more than 5° recurvatum. In the literature recurvatum rates are reported at about 1%. After reviewing all case to date in we did not observe any pin site problems. CAS is still the main objective measure we have in the operating room to date. The advantages of CAS are it provides real time assessment of the true varus/valgus deformity, initial extension and medial/lateral soft tissue imbalance and anticipates final trial reduction. We are performing less soft tissue releases most likely because our tibia and femoral cuts are more precise. Our 10 year follow up data while encouraging requires more investigation

Background. A grossly deformed knee is believed to be an indication for PS -TKA. However, the role CR-TKA in such knees is unclear in the literature. Considering the obvious advantages of CR, we analysed the mid term follow up of CR knees in gross deformities. Materials and Methods. 1590 patients (1740 knees) underwent TKA between January 2011 to December 2012, out of which 570 knees had gross deformity (varus > 15°, FFD > 10°, valgus > 10°, recurvatum > 10). CR-TKA was performed for 540 knees and were included in our study. Subvastus approach was used for all knees. Average age being 68 years, mean BMI being 32 and average weight 70 kgs. Intraoperatively, POLO test was used to ensure PCL stability, further confirmed by direct palpation. Femoral roll-back was found adequate. Results. 95% of grossly deformed knees underwent CR-TKA. Mean pre-operative knee score was 45 which improved to 94 at mid-term follow-up at 18 to 36 months. There were no incidence of component loosening or instability. Three knees needed secondary resurfacing of patella. One knee got infected for which components were explanted and joint debrided thoroughly. Lateral radiographs showed consistent roll-back in all except for 3 knees which had femoral roll-forward. Discussion. PS-TKA have shown to yeild good results in gross deformities, however the role of CR had been unclear. Contrary to popular belief, in our opinion, greater the deformity, greater is the need to retain the PCL. Balancing the flexion extention space is easier and involves lesser resection of distal femur. Hence, its bone preserving. For valgus knees, PCL acts a medial stabilizer. In recurvatum deformity, the posterior capsule being stretched out, retaining PCL has prime importance. Our retrospective mid term follow up have shown good results. However, long term analysis is necessary to highlight the survivorship. Conclusion. CR-TKA must be considered for knees with gross deformity for its aforementioned advantages

The advent of Elastic Stable Intramedullary Nailing has revolutionised the conservative treatment of long human bone fractures in children (Metaizeau, 1988; Metaizeau et al., 2004). Unfortunately, failures still occur due to excessive bending and fatigue (Linhart et al., 1999; Lascombes et al., 2006), bone refracture or nail failure (Bråten et al., 1993; Weinberg et al., 2003). Ideally, during surgery, nail insertion into the diaphyseal medullary canal should not interrupt or injure cartilage growth; nails should provide an improved rigidity and fracture stabilisation. This study aims at comparing deflections and stiffnesses of nail-bone assemblies: standard cylindrically-shaped nails (MI) vs. new cylindrical nails (MII) with a flattened face across the entire length allowing more inertia and a curved tip allowing better penetration into the cancellous bone of the metaphysis (Figure 1). MII exhibits a section with two parameters: a diameter C providing nail stiffness and a height C' providing practical dimension when both nails are crossed at the isthmus of the diaphysis: C/C' is set to 1.25 for all MII nails. A CT scan of a patient aged 22 years was used to segment a 3D model of a 471mm-long right femur model. The medullary canal diameters at the isthmus are 10.8mm and 11.4mm in the ML and AP direction, respectively. Titanium-made CAD models of MI (Ø=4mm) and MII (flat face: Ø=5mm) were pre-curved to maintain their flat face and carefully placed and positioned according to surgeon's instructions. Both nails were inserted via lateral holes in the distal femur with their extremities either bumping against the cortex or lying in the trabecular bone. Transverse and comminuted fractures were simulated (Figure 1). For each assembly, a Finite Element (FE) tetrahedral mesh was generated (∼100181 nodes and 424398 elements). Grey-scale levels were used to assign heterogeneous material properties to the bone (E=6850 ρ. 1.49. (Morgan et al., 2003)). Two modes of loading were considered: 4-point bending (varus and recurvatum: F. max. =6000N) and internal torsion (M. max. =70kNmm). This led to the simulation of 15 FE models, including a reference intact femur. Results show that in valgus, for the transverse (comminuted) fracture, the mean displacement of the assembly decreased by around 50%: from 15.24mm (27.49mm) to 8.15mm (13.85mm) for MI and MII, respectively, compared to 3.59mm for the intact bone. The assembly stiffness increased by 87% and 99% for transverse and comminuted fracture, respectively (Table 1). Similar trends were found in recurvatum with higher increases in assembly stiffness of 170% and 143% for transverse and comminuted fracture, respectively (Table 1). In torsion, for the transverse (comminuted) fracture, the measured angle of rotation decreased from: 0.43rad (0.66rad) to 0.22rad (0.43rad) for MI and MII, respectively, compared to 0.09rad for the intact bone. This corresponded to an increase of 95% and 55% in assembly stiffness for transverse and comminuted fracture, respectively. In conclusion, using the 5mm-diameter new nails (MII) for the same intramedullar space, during either bending or torsion, assemblies were always stiffer than when using standard cylindrical nails

Instability currently represents one of the main causes of residual pain and symptoms following TKA and thus is a major cause of revision total knee replacement, second only to component loosening in some series. Instability related to ligamentous laxity can be categorised by the pattern of relative laxity of the soft tissue structures and this in turn helps in determination of the bony alignment issue, component sizing or positioning problem or ligamentous abnormality that may be contributory and require correction. Instability patterns associated with TKA can be symmetrical and global type instability where there is laxity in all planes, and can also more commonly be asymmetrical or isolated laxity problems where there is good stability in some planes or positions of the knee but excessive laxity in at least one direction. Isolated laxity problems can be subcategorised into one of 3 patterns: Extension instability, Flexion instability, and Recurvatum. Global laxity can occur due to inadequate tibial component thickness, or globally incompetent soft tissues, and can present initially after TKA or alternatively can present late from slow stretch of soft tissues over time as can be seen with some pathologic states. Asymmetrical or Isolated laxity occurs in the sagittal plane when medial vs. lateral “gaps” are unequal and may be due to contracture of tight structures either medially or laterally or can be due to insufficiency or injury of the ligamentous structures on one side vs. the normal structures on other side. Occasionally there is a combination of both contracture on one side and attenuation/stretch on the other side as seen in some patients with severe long standing genu varum or genu valgum. Asymmetrical laxity in the frontal plane generally results in unequal extension vs. flexion “gaps”. This can cause either anteroposterior laxity in flexion but full extension with good stability or alternatively, there may be AP stability in flexion but a lack of full extension in the presence of the exact same pattern of imbalance when a “too thick” polyethylene insert is used to correct what would otherwise be flexion instability. In both cases, the extension gap is tighter than the flexion gap. Isolated recurvatum occurs when the posterior capsular structures are relatively lax or deficient so that a knee that is otherwise stable in the medial-lateral plane in extension, and is stable in the AP plane when in flexion, hyperextends in the fully extended position. In any TKA procedure (but especially revision for instability) it is critical to understand the effect of selected bone resection (or build ups) on soft tissue balancing in order to avoid or treat ligamentous laxity: distal femur – effects extension gap only; posterior femur – effects flexion gap only; proximal tibia – both flexion and extension spaces. During revision for instability, careful evaluation of the cause of the laxity and failure is critically important, especially if there is associated axial deformity or malalignment which generally must be corrected for any reconstruction or revision components to work. Most knees revised for instability issues will require a posterior stabilised or constrained condylar design. Constrained condylar implants are used to compensate for residual medial-lateral imbalance still present after standard soft tissue releases medially (subperiosteal tibia) or laterally (vis selective pie-crust method). However, if the patient displays residual major medial-lateral or global instability that cannot be corrected, or when there is an excessive flexion gap that cannot be stabilised with maximal allowable component sizing, a rotating hinge constrained total knee replacement design may be required. Recent data has shown that rotating hinges can work reliably in restoring stability to the knee in such cases with satisfactory durability and clinical results over time

An important goal of total knee replacement is deformity correction. Arthritic narrowing can be accompanied by a fixed shortening of the collateral ligament on the same side of the narrowing. There can also be ligamentous laxity that develops in the opposite compartment. Flexion contracture can develop with tightening of the posterior capsule. Successful total knee replacement requires proper bone resection along with gap balancing and balanced collateral ligament tensioning. Beware of correctable deformities, as the collateral ligament may have kept its resting length and therefore the knee becomes stable after the bone resections are made and the spacer block is inserted to test the stability of the knee in flexion and extension. In the varus knee, the MCL may be contracted. A medial release of the superficial medial collateral ligament may be necessary. This can be done by stripping the periosteal insertion of the MCL. A stretch may be accomplished by placing a laminar spreader in the narrow medial joint space and opening the space until the MCL stretches from its insertion. This maneuver will require a further increase in polyethylene thickness height of 2 – 4mm. Krackow has also on occasion done a surgical imbrication of the LCL, if it appears attenuated on the lateral side of a severe varus deformity. For valgus deformities, the LCL, arcuate ligament and popliteus and ITB can be contracted. At this time, most authors recommend preservation of the popliteus tendon as it affects primarily the flexion gap. In extension there has been consensus that the surgeon should release what is tight. This may include the ITB release in a pie-crust fashion, or off the Gerdy's tubercle and then a selective release of the arcuate ligament complex. Krackow has also utilised tightening imbrication of the MCL if it is severely attenuated and lax. This has been used infrequently, however. To avoid overlengthening of the knee by referencing balance off of the lengthened, attenuated MCL in cases of severe valgus deformity, less release is performed and a CCK implant may be used. For severe flexion contractures, the posterior osteophytes should be first aggressively removed. The posterior joint capsule can be stripped off the distal femur and sometimes the gastrocnemius muscle insertions can be dissected free. After these maneuvers, proximal raising of the joint line by resection of the distal femur can be utilised. In ankylosis with severe flexion contracture, constrained implants will be needed if the proximal resection extends above the insertion of the collateral ligaments. Recurvatum is a rarely seen deformity that is usually associated with an extraordinarily weak or paretic quadriceps. The joint capsule has become stretched over time. Careful balancing of the knee is necessary. But, if the recurvatum still persists, distally augmenting the femur is an option. And no releases are required

There are many challenges facing the revision knee surgeon. Bony defects, ligamentous imbalance, and difficult gap balancing scenarios are common and require practical management strategies. Typically, an implant with the least amount of constraint necessary to provide a well-aligned, well-balanced arc of motion is preferred. Constraint in implants increases the stresses on both the bearing surfaces and the bony interfaces and may result in earlier mechanical failure of the implant. Despite this fact, there are situations where one cannot rely on a simple larger polyethylene post (such as found in CCK type devices) to balance gaps. The author prefers to choose hinge-type devices in situations that demonstrate massive gap imbalance (typically huge flexion gaps), situations with deficient extensor mechanisms that can result in recurvatum stresses, or in situations of global ligamentous instability. Techniques of supporting the bony interfaces with stems and sleeves may improve the longevity of these constructs. Complications are common, including extensor mechanism problems. Multiple studies have demonstrated reasonable results of hinged implants for these challenging revision scenarios, and the hinge should remain in the armamentarium of the revision surgeon

Aims. A flexed knee gait is common in patients with bilateral spastic cerebral palsy and occurs with increased age. There is a risk for the recurrence of a flexed knee gait when treated in childhood, and the aim of this study was to investigate whether multilevel procedures might also be undertaken in adulthood. Patients and Methods. At a mean of 22.9 months (standard deviation 12.9), after single event multi level surgery, 3D gait analysis was undertaken pre- and post-operatively for 37 adult patients with bilateral cerebral palsy and a fixed knee gait. Results. There was a significant improvement of indices and clinical and kinematic parameters including extension of the hip and knee, reduction of knee flexion at initial contact, reduction of minimum and mean knee flexion in the stance phase of gait, improved range of movement of the knee and a reduction of mean flexion of the hip in the stance phase. Genu recurvatum occurred in two patients (n = 3 legs, 4%) and an increase of pelvic tilt (> 5°) was found in 12 patients (n = 23 legs, 31%). Conclusion. Adult patients with bilateral cerebral palsy and a flexed knee gait benefit from multilevel surgery including hamstring lengthening. The risk of the occurence of genu recurvatum and increased pelvic tilt is lower than has been previously reported in children. Cite this article: Bone Joint J 2017;99-B:1256–64

There are many challenges facing the revision knee surgeon. Bony defects, ligamentous imbalance, and difficult gap balancing scenarios are common and require practical management strategies. Typically, am implant with the least amount of constraint necessary to provide a well-aligned, well-balanced arc of motion is preferred. Constraint in implants increases the stresses on both the bearing surfaces and the bony interfaces and may result in earlier mechanical failure of the implant. Despite this fact, there are situations where one cannot rely on a simple larger polyethylene post (such as found in CCK type devices) to balance gaps. The author prefers to choose hinge type devices in situations that demonstrate massive gap imbalance (typically huge flexion gaps), situations with deficient extensor mechanisms that can result in recurvatum stresses, or in situations of global ligamentous instability. Techniques of supporting the bony interfaces with stems and sleeves may improve the longevity of these constructs. Complications are common, including extensor mechanism problems. Multiple studies have demonstrated reasonable results of hinged implants for these challenging revision scenarios, and the hinge should remain in the armamentarium of the revision surgeon

Introduction. Limb length discrepancy after THA can result in medicolegal litigation. It can create discomfort for the patient and potentially cause back pain or affect the longevity of the implant. Some patients tolerate the length inequality better compared to others despite difference in anatomical femoral length after surgery. Methods and materials. We analyzed the 3D EOS images of 75 consecutive patients who underwent primary unilateral THA (27 men, 48 women). We measured the 3D length of the femur and tibia (anatomical length), the 3D global anatomical length (the sum of femur and tibia anatomical lengths), the 3D functional length (center of the femoral head to center of the ankle), femoral neck-shaft angle, hip-knee-ankle angle, knee flexum/recurvatum angle, sacral slopes and pelvic incidence. We correlated these parameters with the patient perception of the leg length. Results. The values for leg length and pelvic parameters are shown in table 1. 37 patients had a perception of the LLD (49.3%). When the global anatomical length was shorter on the operated side, the perception of the discrepancy was observed in 56% of the cases. In case of anatomical length longer on the operated side, the perception of the discrepancy was described by the patients in 46% of the cases. The LLD perception was correlated with difference in functional length (p=0.0001), pelvic obliquity (p=0.003) and sacral slope (p=0.023). The anatomical femoral length was not correlated with the LLD perception (p=0,008). Discussion. The perception of LLD is a multifactorial complication. We found that the anatomical femoral length (that can be directly affected by the position of the stem) is not the only important factor. The functional length of the lower extremity which can also be affected by the knee deformities is better correlated with the LLD. The pelvic obliquity and version also affect the patient perception of the LLD

Rotating Hinge total knee replacement designs are currently more frequently used for revision total knee replacement. As the designs of these implants have improved over time, the threshold for using them has been lowered. Cases of global instability and severe bone loss have not been adequately addressed by the standard use of unlinked constrained designs. Recurrent dislocation and polyethylene post failure due to cold flow and wear make the use of the unlinked designs insufficient to address the mechanical forces developed in a grossly unstable knee. The linked rotating hinge designs have been able to address global ligamentous instability in four planes. Medial-lateral instability is well addressed by these implants. In cases of severe ankylosis with large flexion contractures, it is often necessary to resect the distal femur above the femoral insertions of the medial and lateral collateral ligaments. The absence of the tethering effect of severely contracted collateral ligaments demand the need for linked designs, although there has been reported success with the use of unlinked designs. Rotating hinges are particularly important for use in cases of recurvatum where an extension stop is incorporated in the design. The design permits slight hyperextension which permits application to clinical situations with incompetent quadriceps strength or paralysis. The clinical results are quite acceptable even though most reports present 65–75% success rates. However, it should also be stated that these patient cohorts represent the most severe cases of revision surgery. Current hinged designs should continue to lower the threshold for use

The femur begins to bow anteriorly at the 200 mm level, but may bow earlier in smaller people. If the stem to be used is less than 200 mm, a straight stem can be used. If the stem is longer than 200 mm, it will perforate the anterior femoral cortex. I know this because I did this on a few occasions more than 20 years ago. To use a long straight stem, there are two techniques. One can either do a diaphyseal osteotomy or one can do a Wagner split (extended trochanteric osteotomy). Both of these will put the knee in some degree of hyperextension, probably insignificant in the elderly, but it may be of significance in the young. In very young people, therefore, it may be preferable to use a bowed stem to avoid this degree of recurvatum. There are two different concepts of loading. Diaphyseal osteotomy implies a proximal loading has been sought. The Wagner split ignores the proximal femur and seeks conical fixation in the diaphysis. There will be very little bone-bone contact between what remains of the attached femur and the detached anterior cortex so that it is important to ensure that the blood supply to the anterior cortex remains intact, preferably by using Wagner's technique, using a quarter-inch osteotome inserted through the vastus to crack the medial cortex. Current modularity is of two types. Distal modularity was attempted many years ago and was never successful. Proximal modularity, as for example, the S-ROM stem, implies various sizes of sleeves fit onto the stem to get a proximal canal fill. In mid-stem modularity, the distal stem wedges into the cone. It has to be driven into where it jams and this can be somewhat unpredictable. For this reason, the solid Wagner stem has been replaced by the mid-stem modular. Once the distal femur is solidly embedded, the proximal body is then selected for height and version. The proximal body is unsupported in the mid-stem modular and initially, few fractures were noted at the taper junction. Cold rolling, shot peening and taper strengthening seem to have solved these problems. There are a variety of types of osteotomy, which can be used for different deformities. With a mid-stem modular system, generally, all that needs to be done is a Wagner-type split and fixation is sought in the mid-diaphysis by conical reaming. No matter what stem is used, distal stability is necessary. This is achieved by flutes, which engage the endosteal cortex. The flutes alone must have sufficient rotational stability to overcome the service loads on the hip of 22 Nm. I divide revision into three categories. In type one, the isthmus is intact, i.e. the bone below the lesser trochanter so that a primary stem can be used. In type two, the isthmus is damaged, i.e. the bone below the lesser trochanter, so a long revision stem is required. In a type three, there is more than 70 mm of missing proximal femur. The Wagner stem may be able to handle this on its own, but most other stems are better supported with a structural allograft cemented to the stem. The reported long term results of mid-stem modular revision implants are good as in most, over 90% survivorship. The introduction of modularity appears to have overcome initial disadvantage of the Wagner stem, i.e. its unpredictability in terms of leg length

Knee replacements may be unstable in the: 1. Plane of motion instability, due to recurvatum or buckling (in flexion). 2. Coronal plane or varus-valgus instability and 3. Flexed position. The third, flexion instability, has been well described and is characterised clinically by early, easy, superior flexion that is then compromised by difficulties with ascending and descending stairs, recurrent effusions and peri-articular tenderness. This “flexion instability” results generally from a flexion gap that is more spacious than the extension gap, where the polyethylene insert has been selected to permit full extension. The term “mid-flexion” instability should not be used as a synonym for “flexion instability”. The concept of mid-flexion instability implies that the knee is stable in extension and stable in flexion (90 degrees) but unstable at points in between. The most common error in assessment probably occurs when surgeons observe stability to varus-valgus stress with the knee locked in full extension, where it is not appreciated that the posterior structures are tight and stabilising the knee. Once the knee if flexed enough to relax these structures, the true “flexion instability is revealed. This is not “mid-flexion” instability. It is conceivable, that an arthroplasty might be designed where the geometry of the femoral condylar curve is such a large, recessed radius that the collateral ligaments are tight in both full extension and 90 degrees of flexion, but unstable in between. There have been marketing allegations that one product or another has been designed in a way to result in “mid-flexion instability. The only published information is based on finite element analysis models. There is scant literature on “mid-flexion” instability”. Laboratory investigations with cadavers, concluded that proximal elevation of the joint line may create “mid-flexion” instability as a result of altering collateral ligament function. Computer models have questioned this effect. One clinical report describes “mid-flexion” (rotational) instability in a revision arthroplasty. So-called “anatomic alignment”, posterior stabilization and resection of distal femur to correct flexion contractures have been alleged to cause “mid-flexion” instability

Stability after TKA is essential for knee function and patient satisfaction. Stability may be marginally more important even than alignment because “stability” means there will be ONE alignment, whereas INSTABILITY means there will be many alignments of the joint, usually the worst one for any loading pattern. Whereas alignment results from the orientation and size of implants, stability depends on all of these, plus soft tissue integrity and in many cases, surgical alteration. Ligament releases (and rarely reconstructions) will certainly be required if alignment is changed with the arthroplasty. Instability may be a subtle or flagrant problem. The “Instabilities” are: . i. Varus- valgus. ii. Plane of motion- Flexion. iii. Plane of Motion-Extension. Varus-valgus instability is the prototype and while it may originate exclusively from the failure of soft tissue, knee alignment and dynamic forces outside the knee joint such as hip abductor dysfunction, scoliois and tibialis posterior rupture may be implicated. A comprehensive approach will be needed. Flexion instability, most simply stated results from a flexion gap that exceeds the dimensions of the extension gap. It will result most commonly after surgery for the patient with a fixed flexion contracture whose knee extends fully because a relatively thin polyethylene insert has been selected. So-called “mid-flexion” instability (implying stability in extension and flexion) has not yet been thoroughly characterised. Extension instability includes all failures of the extensor mechanism (rupture, maltracking and weakness) which are better characterised as “buckling” under a separate topic. Recurvatum has received little attention but can generate the most destructive forces leading to knee arthroplasty failure. In general begins as a compensatory mechanism for relative extensor weakness. All treatment of the unstable TKA must characterise the mode(s) of failure above and correct the underlying cause. Surgical technique will be extremely important, followed eventually by implant selection

Introduction. Coronal misalignment of the lower limbs is closely related to the onset and progression of osteoarthritis. In cases of severe genu varus or valgus, evaluating this alignment can assist in choosing specific surgical strategies. Furthermore, restoring satisfactory alignment after total knee replacement promotes longevity of the implant and better functional results. Knee coronal alignment is typically evaluated with the Hip-Knee-Ankle (HKA) angle. It is generally measured on standing AP long-leg radiographs (LLR). However, patient positioning influences the accuracy of this 2D measurement. A new 3D method to measure coronal lower limb alignment using low-dose EOS images has recently been developed and validated. The goal of this study was to evaluate the relevance of this technique when determining knee coronal alignment in a referral population, and more specifically to evaluate how the HKA angle measured with this 3D method differs from conventional 2D methods. Materials and methods. 70 patients (140 lower extremities) were studied for 2D and 3D lower limb alignment measurements. Each patient received AP monoplane and biplane acquisition of their entire lower extremities on the EOS system according the classical protocols for LLR. For each patient, the HKA angle was measured on this AP X-ray with a 2D viewer. The biplane acquisition was used to perform stereoradiographic 3D modeling. Valgus angulation was considered positive, varus angulation negative. Student's T-test was used to determine if there was a bias in the HKA angle measurement between these two methods and to assess the effect of flexion/hyperextension, femoral rotation and tibial rotation on the 2D measurements. One operator did measurements 2 times. Results. The average total dose for both acquisitions was 0.75mGy (± 0.11mGy). The 2D and 3D measurements are reported in table 1. Intraoperator reliability was >0,99 for all measurements. In the whole series, 2D–3D HKA differences were >2° in 34% of cases, >3° in 22% of cases, >5° in 9% of cases and >10° in 3% of cases >10°. We compared 2D and 3D measurements according to the degree of flessum/recurvatum (> or <5° and > or <10°). The results are reported in table 2. The statistical analysis of parameters influencing 2D/3D measurements is reported in table 3. Discussion and conclusion. The HKA angle is typically assessed from 2D long-leg radiographs. However, several studies highlighted that 2D assessment of this angle may be affected by patient's positioning. Radtke showed that lower limb rotation during imaging significantly affected measurements of coronal plane knee alignment. Brouwer showed that axial rotation had an even greater effect on the apparent limb alignment on AP radiographs when the knee was flexed. This last finding is particularly relevant as many lower extremities present some amount of flexion or hyperextension, especially in aging subjects. This low dose biplanar EOS acquisitions provide a more accurate evaluation of coronal alignment compared to 2D, eliminating bias due to wrong knee positioning. This study points out the interest of EOS in outliers patients and opens new perspectives for preoperative planning and postoperative control of deformity correction or knee joint replacement