Introduction. While the use of stemmed implants is accepted for patients with medial ligament laxity in primary total knee arthroplasty (TKA), the role of stemmed implants in the setting of isolated lateral laxity is unclear. We present a cohort study to assess the effect of unstemmed, constrained TKA for isolated lateral laxity. Methods. 1745 primary TKA performed by the senior surgeon were reviewed. 39 knees in 33 patients with isolated lateral laxity managed with unstemmed components were compared to matched stemmed controls (37 knees in 28 patients). Lateral instability was defined intra-operatively based on >7mm gap in mid-flexion/full extension/figure-of-four with well-positioned components. Primary outcome measures were clinical failure for aseptic loosening (with need for revision as the endpoint) and any radiographic signs of loosening. Results. Average follow-up was 43 months for the unstemmed group (UG) and 25 months for the stemmed group (SG). UG and SG were matched for age, gender, BMI, arthritis etiology, and co-morbidities. The incidence of isolated lateral ligament laxity in this cohort was 4%. There was no difference in clinical outcomes between cohorts. There was no evidence of radiographic loosening; no revisions were performed for aseptic loosening in either group. One SG patient was revised for mid-flexion instability, while one UG patient had an isolated dislocation event without need for revision. Two patients in the UG were treated with incision/debridement and poly-exchange for acute infection. One patient in the SG underwent 2-stage reimplantation. Conclusion. From this data, a post/constraint can be used without stems to compensate for isolated lateral laxity. There is no significant increased risk of loosening with increased constraint, as lateral instability is primarily a swing-phase phenomenon. The goal is limiting varus thrust with improved gait kinematics and patient comfort. Further biomechanical testing and long-term clinical results are needed

Gap balancing technique aims to achieve equal and symmetric gap at full extension and in flexion; however, little is known about the connection between the native and the replaced knee gaps. In this study, a novel robotic assisted ligament tensioning tool was used to measure the pre- and post- operative gaps to better understand their relationship when aiming for balance gaps in flexion and extension. The accuracy of a prediction algorithm for the post-operative gaps based on the native gap and implant alignment was evaluated in this study. The medial and lateral gap were smallest at full extension. The native gaps increase with flexion until 30 degrees where they plateaued for the remaining flexion range. The native lateral gap was larger than the medial gap throughout the flexion range. Planning for equal gaps at extension and flexion resulted with tightest gaps at these angle; however, the gaps in mid-flexion were 3–4 mm larger. Good agreement was observed between the post-operative results and the predicted gas from the software algorithm. The results showed that the native gaps are neither symmetric nor equal. In addition, aiming for equal gaps reduces the variation at these angles but could result in mid- flexion laxity. Advanced robotics-assisted instrumentation can aid in evaluation of soft-tissue and help in surgical planning of TKA. This allows the surgeon to achieve the targeted outcome as well as record the final implant tension to correlate with clinical outcomes.

Conventional computer navigation systems using bone fixation have been validated in measuring anteroposterior (AP) translation of the tibia. Recent developments in non-invasive skin-mounted systems may allow quantification of AP laxity in the out-patient setting.

We tested cadaveric lower limbs (n=12) with a commercial image free navigation system using passive trackers secured by bone screws. We then tested a non-invasive fabric-strap system. The lower limb was secured at 10° intervals from 0° to 60° knee flexion and 100N of force applied perpendicular to the tibial tuberosity using a secured dynamometer. Repeatability coefficient was calculated both to reflect precision within each system, and demonstrate agreement between the two systems at each flexion interval. An acceptable repeatability coefficient of ≤3mm was set based on diagnostic criteria for ACL insufficiency when using other mechanical devices to measure AP tibial translation.

Precision within the individual invasive and non-invasive systems measuring AP translation of the tibia was acceptable throughout the range of flexion tested (repeatability coefficient ≤1.6mm). Agreement between the two systems was acceptable when measuring AP laxity between full extension and 40° knee flexion (repeatability coefficient ≤2.1mm). Beyond 40° of flexion, agreement between the systems was unacceptable (repeatability coefficient >3mm).

These results indicate that from full knee extension to 40° flexion, non-invasive navigation-based quantification of AP tibial translation is as accurate as the standard invasive system, particularly in the clinically and functionally important range of 20° to 30° knee flexion. This could be useful in diagnosis and post-operative follow-up of ACL pathology.

Preoperative ligament laxity can be characterized intraoperatively using digital robotic tensioners. Understanding how preoperative knee joint laxity affects preoperative and early post-operative patient reported outcomes (PROMs) may aid surgeons in tailoring intra-operative balance and laxity to optimize outcomes for specific patients. This study aims to determine if preoperative ligament laxity is associated with PROMs, and if laxity thresholds impact PROMs during early post-operative recovery. 106 patients were retrospectively reviewed. BMI was 31±7kg/m. 2. Mean age was 67±8 years. 69% were female. Medial and lateral knee joint laxity was measured intraoperatively using a digital robotic ligament tensioning device after a preliminary tibial resection. Linear regressions between laxity and KOOS12-function were performed in extension (10°), midflexion (45°), and flexion (90°) at preoperative, 6-week, and 3-month time points. Patients were separated into two laxity groups: ≥7 mm laxity and <7 mm laxity. Student's t-tests determined significant differences between laxity groups for KOOS12-function scores at all time points. Correlations were found between preoperative KOOS12-function and medial laxity in midflexion (p<0.001) and flexion (p<0.01). Patients with <7 mm of medial laxity had greater preoperative KOOS12-function scores compared to patients with ≥7 mm of medial laxity in extension (46.8±18.2 vs. 29.5±15.6, p<0.05), midflexion (48.4±17.8 vs. 32±16.1, p<0.001), and flexion (47.7±18.3 vs. 32.6±14.7, p<0.01). No differences in KOOS12-function scores were observed between medial laxity groups at 6-weeks or 3-months. All knees had <5 mm of medial laxity postoperatively. No correlations were found between lateral laxity and KOOS12-function. Patients with preoperative medial laxity ≥7 mm had lower preoperative PROMs scores compared to patients with <7 mm of medial laxity. No differences in PROMs were observed between laxity groups at 6 weeks or 3 months. Patients with excessive preoperative joint laxity achieve similar PROMs scores to those without excessive laxity after undergoing gap balancing TKA

Abstract. Background. Multi-ligament knee injury is a rare but severe injury. Treatment strategies are challenging for most orthopedic surgeons & optimal treatment remains controversial. The purpose of our study was to assess clinico-radiological and functional outcomes after surgical management of multi-ligament knee injuries & to determine factors that could predict outcome of surgery. Materials And Method. It is a prospective observational study of 30 consecutive patients of Multi-ligament knee injury conducted between 2018–2020. All patients were treated surgically with single-stage reconstruction of all injured ligaments and followed standardized postoperative rehabilitation protocol. All patients were evaluated for Clinical (VAS score, laxity stress test, muscle-strength, range of motion), Radiological (stress radiographs) & Functional (Lysholm score) outcomes three times-preoperatively, post-operative 3 & 12 months. Results. At final follow up mean VAS score was 0.86±0.77. The anteroposterior & valgus-varus stress test showed ligament laxity >10mm (GradeD) in 93.3% patient which improved to <3mm (normal, GradeA) in 90% patients. Most patients (83.3%) had preoperative-range <100° and muscle strength of MRC Grade-3 which improved to >120° and muscle strength of MRC grade-5 at final followup. Lysholm score was poor (<64) in all patients preoperatively and improved to good (85–94) in 73.3%, excellent (>95) in 20% & fair (65–84) in 6.6% patients. The stress radiographs showed stable results for anterior/posterior & varus/valgus stress. All patients returned to their previous work. Factors that could predict outcomes of surgery are age, timing of surgery, type of surgery & associated injury. Conclusion. Early complete single stage reconstruction can achieve good functional results with overall restoration of sports & working capacity. Positive predictive factors for good outcome are younger age, early surgery & appropriate rehabilitation

Patellofemoral instability is common injury and proximal soft tissue stabilisation via MPFL reconstruction or imbrication is the mainstay of treatment. The contribution of certain pathoanatomies to the failure of patellofemoral stabilisation is unknown. The purpose of this study was to analyse the failure rate of patellar stabilisation procedures in a large cohort as measured by re-dislocation of the patella. A secondary purpose was to identify the pathoantomical features that may have predisposed these patients to failure. Between May 2008 and March 2014, 207 MPFL reconstructions and 70 MPFL imbrications were performed by a single surgeon. Post-operative assessment included clinical examination to assess the integrity of the MPFL graft, plain radiographs and the Banff Patellofemoral Instability Instrument (BPII), a disease-specific outcome measure. Failures were identified and risk factors including trochlear dysplasia, patella alta, generalised ligamentous laxity (GLL), femoral tunnel position and rotational abnormalities were evaluated as contributing factors. There were 48 male and 178 female patients. The mean duration of follow-up was 24.1 months (SD 9.4, range 12–74). The average age at time of surgery was 24.81 years (SD 8.87, range 50.35–8.99). The average BMI was 23.75 (SD 3.62, range 36.70–14.90). There were 10 failures in the MPFL reconstruction group (4.8%), 1 male and 9 females. Femoral tunnel position was assessed in relation to Schottle's point as good or excellent in all 10 cases. In terms of pathoanotomy, 8/10 failures had high-grade trochlear dysplasia, 1/10 had patella alta, 6/10 had a Beighton score of >/= 4, and 3/10 had clinically significant rotational abnormalities of the lower extremity. The primary cause attributed to the 10 failure cases was trauma in two, trochlear dysplasia in three, rotational abnormalities in one, combined femoral anteversion and GLL in two, and combined trochlear dysplasia and GLL in two. There were 13 failures in the MPFL imbrication group (18.6%), 2 males and 11 females. Among these failures, 4/13 had high-grade trochlear dysplasia, 3/13 had patella alta, 10/13 had a Beighton score of >/= 4, and one had clinically significant rotational abnormalities of the lower extremity. The primary pathology that was considered to contribute to the imbrication failure cases was trochlear dysplasia in four, generalised ligamentous laxity in six, rotational abnormalities in one, patella alta with trochlear dysplasia in one, and generalised ligamentous laxity with trochlear dysplasia in one. Prior to surgical failure the mean BPII score for the failure group was 71.5/100, compared with 74.6/100 for the remainder of the cohort. MPFL reconstruction is highly successful surgical procedure for stabilising the unstable patella with a failure rate of only 4.8%. Higher failure rates are seen in patients undergoing imbrication of the MPFL compared to a reconstruction. Pathoanatomies that contribute to failure vary between patients with the most common being trochlear dysplasia and generalised ligamentous laxity

This study was performed to assess the incidence of generalised ligament laxity in patients presented with recurrent shoulder dislocations. Prospective data was collected for 38 patients with recurrent shoulder dislocations and 43 patients with clavicle fractures as a control group between May 2007 and July 2009, including demographic details, mechanism of injury, number of dislocations and hyperlaxity. Clinical examination was used to assess the ligament laxity using the Beighton score. The mean age was 29 years with a range from 14-40 years. There were 36 males and 2 females. The left shoulder was involved in 21 patients; right in 13 patients and 4 patients had bilateral shoulder dislocations. The average number of dislocations was 3 with a range from 2-17, while the average number of subluxations was 4.5 with a range from 0-35. The average Beighton score for the patients with recurrent shoulder dislocations was 2.8 with a range from 0-8. 17 patients (45%) in this group had a Beighton score of 4 or more as compared to the control group that had only 12 patients (27%) There was a statistically significant difference between the 2 groups with a P value of < 0.05. 8 patients (21%) fulfilled the Brighton criteria for BJHS. The most common cause of recurrent shoulder dislocation was sports related injuries in 26 patients (68%). The most common sport was football in 14 patients (37%) followed by rugby in 10 (26%) patients. We looked at the incidence of generalised ligament laxity in patients with recurrent shoulder dislocations and found a statistically significant difference as compared with the control group. 21% of the patients fulfilled the Brighton criteria for BJHS but 45% had a Beighton score of 4 or more. Appropriate advice should be given to these patients with hyperlaxity and the timing of shoulder stabilisation should be carefully decided

Background. Calipered kinematically aligned (KA) total knee arthroplasty (TKA) restores the in vitro internal-external (I-E) rotation laxities at 0° and 90° of the native knee. Although increasing and decreasing the thickness of the insert in 1 mm increments loosens and tightens the flexion space, there are little data on how this might adversely affect the screw-home mechanism and I-E rotational laxity. The present study determined the differences in the I-E range of rotation and I-E positions at maximum extension and at 90° of flexion that result from the use of insert thicknesses that deviate ± 1mm in thickness from the implanted insert. Methods. 20 patients were treated with a calipered KA and a PCL retaining implant with a 1:1 medial ball-in-socket constraint and a non-constrained lateral flat articular insert surface. Verification checks, that are validated to restore native tibial compartment forces without release of healthy ligaments including the PCL, were used to select the optimal insert thickness. Trial inserts with thicknesses ranging from 10 to 13 mm were 3-D printed with medial goniometric markings that record rotation from 20° external to −20° internal with respect to a sagittal line laser marked on center of the medial condyle of the trial femoral component at maximum extension and 90° of flexion (Figure 1). Results. For all three inserts, the tibial component progressively internally rotated on the femoral component from maximum extension to maximum flexion. From maximum extension to 90° flexion the −21.7° range of internal rotation for the optimal insert thickness was greater than the −16° for the 1mm thinner insert (p < 0.000), and the −13.1° for the 1mm thicker insert (p < 0.000). At maximum extension, the mean insert position of 7° external for the optimal insert thickness was more external than the 4.5° for the 1mm thinner insert (p < 0.000), and the 3.5° for the 1mm thicker insert (p < 0.000) (Figure 2). At 90° the mean −14.7° internal insert position for the optimal insert thickness was more internal than the −11.5° for the 1mm thinner insert (p < 0.000), and the −9.5° for the 1mm thicker insert (p < 0.000) (Figure 3). Discussion and Conclusions. The insert goniometer is an inexpensive, simple, and sensitive instrument that measured the insert position of a medial ball-in-socket PCL retaining implant with a flat lateral insert implanted with calipered KA and showed the I-E rotation matched the pattern of the native knee's screw-home mechanism. Restoring the pre-arthritic native ligament laxities is the target, as the insert goniometer detected a 6° loss of internal rotation and a less external position of the insert at maximum extension and a less internal position at 90° when the healthy ligaments were stretched or loosened by 1mm. For any figures or tables, please contact the authors directly

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

Introduction. Knee ligament laxity and soft tissue balance are important pre- and intra- operative balancing factors in total knee arthroplasty (TKA). Laxity can be measured pre-operatively from short-leg radiographs using a stress device to apply a reproducible force to the knee, whereas intra-operative laxity is routinely measured using a navigation system in which a variable surgeon-applied force is applied. The relationship between these two methods and TKA outcome however, has not been investigated. This study aims to determine how intra-operative assessments of laxity relate to functional radiographic assessments performed on pre-operatively. We also investigate how laxity relates to short-term patient-reported outcomes. Method. A prospective consecutive study of 60 knees was performed. Eight weeks prior to surgery, patients had a CT scan and functional radiographs captured using a Telos stress device (Metax, Germany). This device applies a force to the knee joint while bracing the hip and ankle causing either a varus or valgus response. 3D bone models were segmented from the CT scan and landmarked to generate patient specific axes and alignments. Individual bone models were registered to the 2D stressed X-rays in flexion and extension. Reference axes identified on the registered 3D bone models were used to measure the coronal plane laxity. These laxity ranges were compared with those measured by a navigation system (OMNINAV, OMNI Life Science, MA) used during surgery, and Knee Injury and Osteoarthritis Outcome Scores (KOOS) captured 6 months postoperatively. Results. Laxity measurements were acquired from 54 patients (58 knees; 4 bilaterals). The average age was 65±15 years old and 57% (n=31) of the patients were female. The midpoints of the laxity curves generated by Telos and navigation techniques show significant strong correlations in extension (r = 0.83, p < 0.001) and flexion (r = 0.53, p < 0.001). However, the laxity ranges measured by the two techniques did not. On average the navigation system produced significantly larger laxity range measurements than the Telos stressed x- ray technique in both extension (Nav: 8.4° ± 2.0°; Telos: 4.0° ± 2.4°; p < 0.001) and flexion (Nav: 5.0 ± 2.4; Telos: 3.0 ± 2.4; p < 0.001). Telos-generated laxity ranges indicate that patients who have initially greater laxity in extension than flexion (laxity range difference > 2°) have significantly better 6-month pain KOOS than those who show greater laxity in flexion (laxity range difference < −2°) (p = 0.018), see Figure 1. This correlation does not hold however, when examining laxity ranges generated by the navigation system, see Figure 2. Discussion and Conclusions. Significantly larger navigation-generated laxity ranges may be caused by: variable forces applied by the surgeon while the patient is under anaesthetic, surpassing the patient's functional limit; as well as due to the altered physical state of the knee during surgery. More sophisticated techniques to reproducibly assess intra-operative soft tissue balance may be required to accurately define laxity range. Results indicate that functional Telos-generated laxity ranges may provide unique insight into the relationship between laxity and postoperative outcomes that cannot be attained with passive navigated measurements

Pre-operative planning in revision total knee replacement is important to simplify the surgery for the implant representative, operating room personnel and the surgeon. Revision knee arthroplasty is performed for many different reasons and of variable complexity. Many implant options can be considered including cemented and cementless primary and stemmed revision tibial and femoral components, with posterior cruciate retention or resection, and either with no constraint, varus/valgus constraint, or with rotating hinge bearings. One may also need femoral and tibial spacers, metaphyseal augments, or bulk allograft. It is important to pre-operatively determine which of these implants you may need. If you schedule a revision total knee and ask the implant representative to “bring everything you've got, just in case,” they will have to bring a truck full of instruments and implants. The first step of pre-operative planning is to determine how much implant constraint will be needed. Survivorship of revision total knees with modern varus/valgus constrained or rotating hinge implants are not that unacceptable. Ideally to enhance longevity, the least constraint needed should be used. This requires determination of the status of the ligaments. Varus and valgus stress is applied to the knee in near full extension, mid-flexion, and ninety degrees of flexion. If instability of the knee is noted, then radiographs are reviewed to determine if component malposition or malalignment is the reason for the collateral ligament laxity. If radiographs don't show a reason, then have additional constraint available in case the knee can't be balanced with proper component position and ligament balancing. In cases other than simple revisions, the posterior cruciate ligament is usually inadequate or needs to be resected to balance the knee. Substitution for the posterior cruciate ligament is usually needed for most revisions. The second step of pre-operative planning is to review radiographs to determine the amount and location of any bone loss. Osteolysis induced bone loss is usually worse than seen on plain radiographs. If unsure, a CT scan can be of help. The presence of significant bone loss contraindicates the use of primary components and mandates the need for stemmed implants. Larger defects may warrant having metallic augments or bulk graft present. Most revision knee implants can be conservatively metaphyseal cemented with diaphyseal engaging press-fit stems. The third step of pre-operative planning is to be familiar with what implants are present. Occasionally, one may not need to revise components that are stable and well aligned. Having compatible components available may simplify the surgery. Excellent pre-operative planning will minimise the need to bring in an excessive number of instruments and implants. It will help assure that the patient has a stable revision knee and simplify the surgery for all participants

Aims

As an alternative to external fixators, intramedullary lengthening nails (ILNs) can be employed for distraction osteogenesis. While previous studies have demonstrated that typical complications of external devices, such as soft-tissue tethering, and pin site infection can be avoided with ILNs, there is a lack of studies that exclusively investigated tibial distraction osteogenesis with motorized ILNs inserted via an antegrade approach.

Deformity correction is a fundamental goal in total knee arthroplasty. Severe valgus deformities often present the surgeon with a complex challenge. These deformities are associated with abnormal bone anatomy, ligament laxity and soft tissue contractures. Distorted bone anatomy is due to bone loss on the lateral femoral condyle, especially posteriorly. To a lesser extent bone loss occurs from the lateral tibia plateau. The AP axis (Whiteside's Line) or epicondylar axis must be used as a rotational landmark in the severely valgus knee. Gap balancing techniques can be helpful in the severely valgus knee, but good extension balance must be obtained before setting femoral rotation with this technique. Coronal alignment is generally corrected to neutral or 2- to 3-degree overcorrection to mild mechanical varus to unload the attenuated medial ligaments. The goal of soft tissue releases is to obtain rectangular flexion and extension gaps. Soft tissue releases involve the IT band, posterolateral corner/arcuate complex, posterior capsule, LCL, and popliteus tendon. Assessment of which structures is made and then releases are performed. In general, pie crust release of the IT band is sufficient for mild deformity. More severe deformities require release of the posterolateral corner / arcuate and posterior capsule. I prefer a pie crust technique, while Ranawat has described the use of electrocautery to perform these posterior/ posterolateral releases. In most cases the LCL is not released, however, this can be released from the lateral epicondyle, if necessary. Good ligament balance can be obtained in most cases, however, some cases with severe medial ligament attenuation require additional ligament constraint such as a constrained condylar implant

Down syndrome (DS), is a genetic disorder caused by a third copy of the 21st chromosome (Trisomy 21), featuring typical facial characteristics, growth delays and varying degrees of intellectual disability. Some degree of immune deficiency is variably present. Multiple orthopaedic conditions are associated, including stunted growth (90%), ligamentous laxity (90%), low muscle tone (80%), hand and foot deformities (60%), hip instability (30%), and spinal abnormalities including atlanto-axial instability (20%) and scoliosis. Hip disease severity varies and follows a variable time course. Rarely a child presents with DDH, but during the first 2 years the hips are characteristically stable but hypermobile with well-formed acetabulae. Spontaneous subluxation or dislocation after 2 presents with painless clicking, limping or giving way. Acute dislocation is associated with moderate pain, increased limp and reduced activity following minor trauma. Hips are reducible under anesthesia, but recurrence is common. Eventually concentric reduction becomes rarer and radiographic dysplasia develops. Pathology includes: a thin, weak fibrous capsule, moderate to severe femoral neck anteversion and a posterior superior acetabular rim deficiency. A number of femoral and acetabular osteotomies have been reported to treat the dysplasia, with acetabular redirection appearing to be most successful. However, surgery can be associated with a relatively high infection rate (20%). Additionally, symptomatic femoral head avascular necrosis can occur as a result of slipped capital femoral epiphysis. Untreated dysplasia patients can walk with a limp and little pain into the early twenties even with fixed dislocation. Pain and decreasing hip function is commonly seen as the patient enters adult life. Occasionally the hip instability begins after skeletal maturity. Total hip arthroplasty (THA) is the standard treatment when sufficient symptoms have developed. The clinical outcomes of 42 THAs in patients with Down syndrome were all successfully treated with standard components. The use of constrained liners to treat intra-operative instability occurred in eight hips and survival rates were noted between 81% and 100% at a mean follow-up of 105 months (6 – 292 months). A more recent study of 241 patients with Down syndrome and a matched 723-patient cohort from the Nationwide Inpatient Sample compared the incidence of peri-operative medical and surgical complications in those who underwent THA. Compared to matched controls, Down syndrome patients had an increased risk of complications: peri-operative (OR, 4.33; P<.001), medical (UTI & Pneumonia OR, 4.59; P<.001) and surgical (bleeding OR, 3.51; P<.001), Mean LOS was 26% longer (P<.001). While these patients can be challenging to treat, excellent surgical technique and selective use of acetabular constraint can reliably provide patients with excellent pain-relief and improved function. Pre-operative education of all clinical decision makers should also reinforce the increased risk of medical and surgical complications (wound hemorrhage), and lengths of stay compared to the general population

Background. Extensive research has previously been conducted analyzing the biomechanical effects of rotational changes (i.e. version and inclination) of the acetabular cup. Many sources, citing diverse dislocation statistics, encourage surgeons to strive for various “safe zones” during the THA operation. However, minimal research has been conducted, especially under in vivo conditions, to assess the consequences of cup translational shifting (i.e. offsets, medial and superior reaming, etc.). While it is often the practice to medialize the acetabular cup intraoperatively, there is still a lack of information regarding the biomechanical consequences of such cup medializations and medial/superior malpositionings. Objective. Therefore, the objective of this study is to use a validated forward solution mathematical model to vary cup positioning in both the medial and superior directions to assess simulated in vivo kinematics. Methods. The model used for this study has been validated with telemetric data and incorporates numerous muscles and ligaments. The model is parametrically derived and allows the user to simulate a theoretical THA surgery and to assess the outcomes of proper positioning as well as malpositioning of the cup. Parameters of interest in this study are component positions, joint instability and sliding, and contact area. Results. An intraoperative representation of the pelvis and cup was assessed (Figure 1), with a green star showing the native anatomical center, the red circle showing the acetabular cup center, and the arrow representing the reaming direction. During swing phase, it was determined that unaccounted for acetabular cup shifting of 5–10 mm leads to capsular ligament laxity coupled with an increase in hip joint instability. Two swing phase scenarios were assessed, one simulating adequate capsular tension and therefore a uniform contact patch and the other simulating inadequate capsule tension and therefore femoral component pistoning with a smaller contact patch (Figure 2). During stance phase, it was determined that acetabular cup shifting of 5–10 mm in the medial and/or superior directions yields an increase in hip joint instability. Two stance phase scenarios were simulated, one yielding no hip separation and therefore a uniform, centralized contact patch, and the other yielding ∼1.5 mm of hip separation and therefore a non-uniform, supero-lateral edge loading patch (Figure 3). Cup orientation does not appear to directly cause hip instability, but it will either lessen or exacerbate the instability, depending on the specific scenario. The results in this study did reveal that overly-inclined cups will yield less stability in the lateral direction, and overly-anteverted cups will yield less stability in the anterior direction. Discussion. In general, instability during stance phase comes in the form of femoral head sliding and edge loading, and instability during swing phase comes in the form of femoral head pistoning. This study's analyses did reveal that proper alignment of the acetabular cup is required for ideal clinical results. The results from this study dictate that proper translational alignment of the cup as well as rotational alignment is necessary for patient stability and proper hip mechanics. For any figures or tables, please contact authors directly

Deformity correction is a fundamental goal in total knee arthroplasty. Severe valgus deformities often present the surgeon with a complex challenge. These deformities are associated with abnormal bone anatomy, ligament laxity and soft tissue contractures. Distorted bone anatomy is due to bone loss on the lateral femoral condyle, especially posteriorly. To a lesser extent bone loss occurs from the lateral tibia plateau. The AP Axis (Whiteside's Line) or Epicondylar axis must be used as a rotational landmark in the severely valgus knee. Gap balancing techniques can be helpful in the severely valgus knee, but good extension balance must be obtained before setting femoral rotation with this technique. Coronal alignment is generally corrected to neutral or 2- to 3-degree overcorrection to mild mechanical varus to unload the attenuated medial ligaments. The goal of soft tissue releases is to obtain rectangular flexion and extension gaps. Soft tissue releases involve the IT band, Posterolateral Corner/Arcuate Complex, Posterior Capsule, LCL, and Popliteus Tendon. Assessment of which structures is made and then releases are performed. In general Pie Crust release of the ITB is sufficient for mild deformity. More severe deformities require release of the Posterolateral Corner/Arcuate Complex and Posterior Capsule. I prefer a pie crust technique, while Ranawat has described the use of electrocautery to perform these posterior/ posterolateral releases. In most cases the LCL is not released, however, this can be released from the lateral epicondyle, if necessary. Good ligament balance can be obtained in most cases, however, some cases with severe medial ligament attenuation require additional ligament constraint such as a constrained condylar implant

Dislocation is a particular problem after total hip replacement in femoral neck fractures and elderly, especially female, patients. The increased rate of dislocation in this population is probably due to significant ligamentous laxity in these patients and poor coordination and proprioception. Another population of patients with increased propensity for dislocation is the revision hip replacement patient. Current dislocation rates in these patients can approach 10% with conventional implant systems. The Dual Mobility total hip system is composed of a cobalt chrome acetabular shell that has a grit blasted, beaded and/or hydroxyapatite coating to improve bone ingrowth. The polyethylene liner is highly crosslinked polyethylene and fits congruently into the cobalt chrome shell and acts like a large femoral head (usually > 40 mm). The femoral head attached to the trunnion is usually 28 mm. The femoral head snaps into the polyethylene liner to acts as a second protection against dislocation. Indications for the Dual Mobility socket are in the high risk for dislocation patient and particularly in elderly, female patients. It is also indicated in patients with neuromuscular disease who are at more risk to dislocate. To date 237 dual mobility cups have been performed with an average age of 79 and 207 of the procedures in women. The follow up extends to 5.6 years with an average of 3.5. There has been 1 dislocation which occurred after a traumatic event. There have been no mechanical failures, no infections and no other revisions in this series. Interprosthetic dislocation has been reported in long term follow up and there was, in this series, when reduction was performed on the only liner dislocation. Pain relief has been no different than conventional hip replacement and range of motion is unchanged as well

Dislocation is a particular problem after total hip replacement in femoral neck fractures and elderly especially female patients. The increased rate of dislocation in this population is probably due to significant ligamentous laxity in these patients and poor coordination and proprioception. Another population of patients with increased propensity for dislocation is the revision hip replacement patient. Current dislocation rates in these patients can approach 10% with conventional implant systems. The Dual Mobility total hip system is composed of a cobalt chrome acetabular shell with a grit blasted, beaded and/or hydroxyapatite coating to improve bone ingrowth. The polyethylene liner is highly cross-linked polyethylene and fits congruently into the cobalt chrome shell and acts like a large femoral head (usually >40mm). The femoral head attached to the trunnion is usually 28mm or 32mm. The femoral head snaps into the polyethylene liner to acts as a second protection against dislocation. Indications for the Dual Mobility socket are in the high risk for dislocation patient and particularly in elderly female patients. One hundred fifty-six patients with an average age of 79 have been performed to date with a maximum follow up to 4.2 years. To date there have been no mechanical or septic failures and no dislocations. Pain relief has been no different than conventional hip replacement and range of motion is unchanged as well. There have been reported cases of intraprosthetic dislocation but these have not occurred to date

Deformity can be associated with significant bone loss, ligament laxity, soft-tissue contractures, distortion of long bone morphology, and extra-articular deformity. Correction of varus, valgus, or flexion deformity requires soft tissue releases in conjunction with bone cuts perpendicular to the long axes of the femur and tibia. Cruciate-retaining or -substituting implants can be used based on surgeon preference if the ligaments are well balanced. However, in presence of severe deformity, additional measures may be warranted to achieve alignment and balance. TKA then becomes a more challenging proposition and may require the surgeon to perform extensive releases, adjunct osteotomies and deploy more constrained implants. Merely enhancing constraint in the implant however without attending to releases and extra-articular correction may not suffice. Certain myths in deformity correction will be presented. Technical tips with regard to preoperative planning, i.e., whether intra-articular correction alone will suffice or extra-articular correction is required, will be highlighted. Surgical principles and methods of performing large releases, reduction osteotomy, lateral epicondylar sliding osteotomy, sliding medial condylar osteotomy, and closed wedge diaphyseal/metaphyseal osteotomy concomitantly with TKA will be illustrated with examples. Technique of performing TKA with concomitant extra-articular deformity resulting from coronal bowing of femoral or tibial diaphysis, malunited fractures, prior osteotomies, and stress fractures will be presented. The techniques reported can successfully restore alignment, pain-free motion, and stability without necessarily using more constrained implants

Deformity can be associated with significant bone loss, ligament laxity, soft-tissue contractures, distortion of long bone morphology, and extra-articular deformity. Correction of varus, valgus, or flexion deformity requires soft tissue releases in conjunction with bone cuts perpendicular to the long axes of the femur and tibia. Cruciate-retaining or -substituting implants can be used based on surgeon preference if the ligaments are well balanced. However, in presence of severe deformity, additional measures may be warranted to achieve alignment and balance. TKA then becomes a more challenging proposition and may require the surgeon to perform extensive releases, adjunct osteotomies and deploy more constrained implants. Merely enhancing constraint in the implant, however, without attending to releases and extra-articular correction may not suffice. Pre-operative planning, i.e., whether intra-articular correction alone will suffice or extra-articular correction is required, will be highlighted. Surgical principles and methods of performing large releases, reduction osteotomy, lateral epicondylar sliding osteotomy, sliding medial condylar osteotomy, and closed wedge diaphyseal/metaphyseal osteotomy concomitantly with TKA will be illustrated with examples. Results of a large series of TKA with extra-articular deformity resulting from coronal bowing of femoral or tibial diaphysis, malunited fractures, prior osteotomies, and stress fractures will be presented. The techniques reported can successfully restore alignment, pain-free motion, and stability without necessarily using more constrained implants