Functional knee apparatus for the evaluation of ligamentous tensions on contact loads.

BACKGROUND: Soft tissue balancing is integral in providing stability following total knee arthroplasty (TKA). Although intraoperative contact load sensors are providing insights into the effects of soft tissue balancing, there is still a lack of understanding of the relationship between the knee's ligamentous tensions and joint surface contact loads. This study reports on the development of a multifunctional testing apparatus that can quantify the effects of ligamentous tension on joint contact loads in a controlled repeatable environment. METHODS: The functional knee apparatus was constructed to act as an anatomical substitute for the benchtop assessment of intraoperative soft tissue balancing. The system was calibrated through reproduction of results from a cadaveric study that employed intraoperative load sensors. Experimentation was then conducted to quantify the effects of tensile pretension variation on measured contact loads throughout the full range of flexion. RESULTS: A linear relationship between the ligamentous tensions and contact loads was observed, with ligaments contributing to 74-80% of the measured contact loads. Ligamentous tensions could be approximated from measured contact loads to within ± 23 N. CONCLUSION: The proposed apparatus can prove to be a valuable tool in the continued exploration of currently undocumented effects (e.g. surgical alteration) in soft tissue balancing. In addition to quantifying the relationship between ligamentous tensions and joint contact loads, soft tissue loading conditions where bicondylar contact was lost (i.e. known sign of kinematic instability) were identified. As a corollary, this system may be able to provide insights on soft tissue balancing standards predictive of patient outcomes.

Technology Applications for Arthroplasty: Moving the Field Forward?

Total joint arthroplasty (TJA) is one of the most performed and successful surgeries in the United States for advanced degenerative and inflammatory arthritis with most patients reporting excellent outcomes. However, a large number of patients are still dissatisfied following TJA. To improve outcomes, new technologies such as patient-specific instrumentation and custom implants; smart implant trials; radiologic, computer, and portable accelerometer-based navigation systems; and robotics have been developed. Their overall goals are to avoid the drawbacks of conventional arthroplasty surgery, to simplify the procedures, to improve the accuracy of surgical techniques, to improve outcomes, and to decrease costs. This chapter provides an overview of the current technologies and their applications in TJA.

Relationship between surgical balancing and outcome measures in total knees.

BACKGROUND: The purpose of the study was to investigate the accuracy of balancing which could be achieved at total knee surgery and its relation to functional outcomes. METHODS: During surgery, the forces on the medial and lateral plateaus were measured at 10-15 degrees flexion in 101 patients, using an instrumented tibial trial, with equal forces being targeted. Of the initial 101 cases, 71 cases completed all follow-up visits to 1 year. At each follow-up visit, the function was measured using the Knee Society Scoring System, and varus and valgus laxity angles were measured. RESULTS: The mean medial/(medial + lateral) compartmental force ratio was 0.52, with a standard deviation of 0.09. The total contact force was 217 Newtons, with a standard deviation of 72 Newtons. No correlations were found between the functional scores and the compartmental force ratio or total contact force. However, the mean varus and valgus laxity angles, 2.8 and 2.3 degrees, respectively, were very close to the angles of normal intact knees. CONCLUSIONS: The likely reason for the lack of correlation of function was that the large majority of the balancing ratios were within the range 0.4-0.6 but with a wide spread of functional scores typical of total knee study groups. However, the normal varus and valgus angles achieved at follow-up indicated that equal balancing in early flexion was a reasonable surgical target. Using instrumented tibial trials enabled accurate and consistent balancing values to be achieved, as well as normal varus and valgus laxity angles, which may be important in obtaining optimal outcomes.

Tramadol in Knee Osteoarthritis: Does Preoperative Use Affect Patient-Reported Outcomes After Total Knee Arthroplasty?

BACKGROUND: The 2013 American Academy of Orthopedic Surgeons evidence-based guidelines recommend against the use of preoperative narcotics in the management of symptomatic osteoarthritic knees; however, the guidelines strongly recommend tramadol in this patient population. To our knowledge, no study to date has evaluated outcomes in patients who use tramadol exclusively as compared with narcotics naive patients. METHODS: This is a retrospective study of prospectively collected data for patients who underwent unilateral primary total knee arthroplasty between January 2017 and March 2018. PRO scores were obtained using a novel electronic patient rehabilitation application, which pushed PRO surveys via email and mobile devices within 1 month prior to surgery and 3 months postoperatively. RESULTS: One hundred and thirty-six patients were opiate naïve, while 63 had obtained narcotics before the index operation. Of those, 21 patients received tramadol. The average preoperative Knee Disability and Osteoarthritis Outcome Scores were 50.4, 49.95, and 48.01 for the naïve, tramadol, and narcotic populations, respectively, (P = .60). The tramadol cohort had the least gain in 3 months postoperative Knee Disability and Osteoarthritis Outcome Scores, improving on average 12.5 points in comparison to the 19.1 and 20.1 improvements seen in the narcotic and naïve cohorts, respectively (P = .09). This difference was statistically significant when comparing the naïve and tramadol populations alone in post hoc analysis (P = .016). CONCLUSIONS: When comparing patients who took tramadol preoperatively to patients who were opiate naïve, patients that used tramadol trended toward significantly less improvement in functional outcomes in the short-term postoperative period.

Payer type does not impact patient-reported outcomes after primary total knee arthroplasty.

BACKGROUND: There is a paucity of literature assessing whether payer type has an impact on postoperative patient-reported outcomes (PROs) after total knee arthroplasty (TKA). The aim of this study was to comparatively evaluate TKA PROs among patients with commercial and Medicare insurance. METHODS: We conducted a single-center, retrospective review of patients operated between January 2017 and March 2018. Knee Disability and Osteoarthritis Outcome Score Junior (KOOS-Jr) and Veterans RAND 12 Health Survey (VR-12) Physical Component (VR-12 PCS) and Mental Component (VR-12 MCS) PRO scores were collected prospectively at baseline and 12 weeks postoperatively via an electronic patient rehabilitation application. Univariable and multivariable linear regressions were utilized to assess the effects of patient insurance type on PRO. RESULTS: In total, 193 TKA candidates had commercial (n = 91) or Medicare (n = 102) as their primary payer type. Demographic variables including age, gender, body mass index, and race varied significantly between the cohorts (P < .05). Length of stay and discharge disposition also varied significantly (P < .05). When compared with commercial payers, Medicare beneficiaries demonstrated a 4.13 ± 2.06 increase in Knee Disability and Osteoarthritis Outcome Score JR. scores at baseline (P < .05). However, after adjusting for patient-specific demographic and perioperative variables, all PROs recorded in this study were similar between the 2 payer groups at baseline and 12 weeks postoperatively (P > .05). Furthermore, ΔPRO scores from baseline to 12 weeks were also similar (P > .05). CONCLUSIONS: After adjusting for patient-specific variables, PROs are similar at baseline and 12 weeks postoperatively between commercial and Medicare cohorts. For TKA candidates with similar baseline demographics, surgeons can expect similar perioperative PROs regardless of insurance type.

Relationship Between Ligament Forces and Contact Forces in Balancing at Total Knee Surgery.

BACKGROUND: Spacer blocks, tensors, or instrumented tibial trials are current methods of balancing the knee during surgery but there are no current techniques for measuring ligament forces. Our goal was to study the relationship between the collateral ligament forces and the condylar contact forces to determine whether there was equivalence. METHODS: A test rig was constructed modeling an artificial knee joint with collateral ligaments. The ligament forces as well as the lateral and medial tibial contact forces were measured during flexion for different positions of the femoral component on the femur, producing a set of forces for the simulated conditions. A regression analysis was used to study the correlation between the ligament and contact forces. RESULTS: The combined medial and lateral ligament and contact forces showed a linear relation with a correlation coefficient of 0.98. For the medial and lateral sides separately, the correlations were 0.85 and 0.88, respectively, with more than 80% of points within a ±25% deviation from the linear relations. This deviation from the linear correlation is linked to differences in medial-lateral femoral-tibial contact point locations at different flexion angles. CONCLUSION: Within balancing accuracies generally achieved at surgery, the collateral ligament forces were linearly correlated to the condylar contact forces. These forces can also be equally correlated to the distraction forces as well as the moments at which condylar liftoff would occur from varus-valgus moments. This indicated a unification of the different balancing parameters, and hence such quantitative methods can be used interchangeably.

Laxity and contact forces of total knee designed for anatomic motion: A cadaveric study.

BACKGROUND: Total knee designs that attempt to reproduce more physiological knee kinematics are gaining attention given their possible improvement in functional outcomes. This study examined if a total knee designed for anatomic motion, where the soft tissue balancing was intended to replicate anatomical tibiofemoral contact forces, can more closely reproduce the laxity of the native knee. METHODS: In an ex-vivo setting, the laxity envelope of the knees from nine lower extremity specimens was measured using a rig that reproduced surgical conditions. The rig allowed application of a constant varus/valgus (V/V) and internal-external (I/E) torque through the range of motion. After testing the native knee, total knee arthroplasty (TKA) was performed using the Journey II bi-cruciate substituting implant. Soft tissue balancing was guided by targeting anatomical compressive forces in the lateral and medial tibiofemoral joints with an instrumented tibial trial. After TKA surgery, the laxity tests were repeated and compared to the native condition. RESULTS: The TKA knee closely reproduced the coronal laxity of the native knee, except for a difference at 90° of flexion for valgus laxity. Looking at the rotational laxity, the implant constrained the internal rotation relative to the native knee at 45 and 60° of flexion. The forces on the tibial trial for the neutral path of motion showed higher values on the medial side as the knee flexed. CONCLUSIONS: This study suggested that when using an anatomically-designed knee, the soft tissue balancing should also aim for anatomical contact forces, which will result in close to normal laxity patterns.

Contact forces in the tibiofemoral joint from soft tissue tensions: Implications to soft tissue balancing in total knee arthroplasty.

Proper tension of the knee's soft tissue envelope is important during total knee arthroplasty; incorrect tensioning potentially leads to joint stiffness or instability. The latter remains an important trigger for revision surgery. The use of sensors quantifying the intra-articular loads, allows surgeons to assess the ligament tension at the time of surgery. However, realistic target values are missing. In the framework of this paper, eight non-arthritic cadaveric specimens were tested and the intra-articular loads transferred by the medial and lateral compartment were measured using custom sensor modules. These modules were inserted below the articulating surfaces of the proximal tibia, with the specimens mounted on a test setup that mimics surgical conditions. For both compartments, the highest loads are observed in full extension. While creating knee flexion by lifting the femur and flexing the hip, mean values (standard deviation) of 114N (71N) and 63N (28N) are observed at 0° flexion for the medial and lateral compartment respectively. Upon flexion, both medial and lateral loads decrease with mean values at 90° flexion of 30N (22N) and 6N (5N) respectively. The majority of the load is transmitted through the medial compartment. These observations are linked to the deformation of the medial and lateral collaterals, in addition to the anatomy of the passive soft tissues surrounding the knee. In conclusion, these findings provide tangible clinical guidance in assessing the soft tissue loads when dealing with anatomically designed total knee implants.

Rigid Patient Positioning is Unreliable in Total Hip Arthroplasty.

BACKGROUND: To our knowledge, no study has assessed the ability of rigid patient positioning devices to afford arthroplasty surgeons with ideal acetabular orientation throughout surgery. The purpose of this study is to use robotic arm-assisted computer navigation to assess the reliability of pelvic position in total hip arthroplasty performed on patients positioned with rigid positioning devices. METHODS: A prospective cohort of 100 hips (94 patients) underwent robotic-guided total hip arthroplasty in the lateral decubitus position from the posterior approach, 77 stabilized by universal lateral positioner, and 23 by peg board. Before reaming, computed tomography-templated computer software generated true values of pelvic anteversion and inclination based on the position of the robot arm registered to the patient's preoperative pelvic computed tomography. RESULTS: Mean alteration in anteversion and inclination values was 1.7° (absolute value, 5.3°; range, -20° to 20°) and 1.6° (absolute value, 2.6°; range, -8° to 10°), respectively. And 22% of anteversion values were altered by >10° and 41% by >5°. There was no difference between hip positioners used (P = .36). Anteversion variability was correlated with body mass index (P = .02). CONCLUSION: Despite the use of rigid patient positioning devices-a lateral hip positioner or peg board-this study reveals clinically important malposition of the pelvis in many cases, especially with regard to anteversion. These results show a clear need to pay particular attention to anatomic landmarks or computer-assisted techniques to assure accurate acetabular cup positioning. Patient positioning should not be solely trusted.

Accuracy of Balancing at Total Knee Surgery Using an Instrumented Tibial Trial.

BACKGROUND: Balancing is an important part of a total knee procedure, and in recent years, more emphasis has been given to quantifying the process. METHODS: During 101 total knee surgeries, initial bone cuts were made using navigation. Lateral and medial contact forces were determined throughout flexion using an instrumented tibial trial. Balancing was defined as a ratio of the medial and total force, the target being 0.5 (equal lateral and medial forces). Based on the initial values, surgical corrections were selected to achieve balancing. The most common corrections were soft tissue releases (63 incidences), including MCL, posterolateral corner, posteromedial corner, and changing tibial insert thicknesses (34 incidences). RESULTS: After final balancing, the mean ratio was 0.52 ± 0.14, between 0.35 and 0.65 being achieved in 80% of cases. In 84% of cases, only 0-2 corrections were required. The average total force on the condyles was 215 ± 86 N. CONCLUSION: Our study provides data to surgeons on the results to expect when balancing a knee, which can enhance both accuracy and consistency of the procedure.

Incidence of patellar clunk syndrome in fixed versus high-flex mobile bearing posterior-stabilized total knee arthroplasty.

The geometry of the intercondylar box plays a significant role in the development of patellar clunk syndrome. We reviewed the incidence of patella clunk at mid-to-long-term follow-up of a rotating high-flex versus fixed bearing posterior stabilized TKA design. 188-mobile and 223-fixed bearing TKAs were reviewed for complications, incidence of patellar clunk, treatment, recurrence rates, range of motion, and patient satisfaction. Patellar clunk developed in 22 knees in the mobile (11.7%) and in 4 (1.8%) in the fixed bearing group (P<0.001). 23 out of 26 cases resolved with a single arthroscopic treatment and 2 resolved with a second procedure. The mean postoperative range of motion was 122.4°. All but one patient reported overall satisfaction with the index procedure. In contrast with other recent studies we found a significant incidence of patellar clunk in high-flex mobile bearings. Despite the high rate of patellar clunk syndrome, overall patients did well and were satisfied with their outcomes.

Effects of surgical variables in balancing of total knee replacements using an instrumented tibial trial.

BACKGROUND: In total knee surgery, typically the bone cuts are made first to produce the correct overall alignment. This is followed by balancing, often using spacer blocks to obtain equal parallel gaps in flexion and extension. Recently an electronically instrumented tibial trial has been introduced, which measures lateral and medial contact forces. The goal of our study was to determine the effect of different surgical variables; changing component sizes, modifying bone cuts, or ligament releases; on the contact forces, as a method to achieve balancing. METHODS: A special rig was designed to fit on a standard operating table, on which tests on 10 lower extremity specimens were carried out. After making bone cuts for a posterior cruciate retaining knee using a navigation system, tibial thickness was determined in extension using the Sag Test. Different Surgical Variables were then implemented, and the changes in the condylar forces were determined throughout flexion using the Heel Push Test. RESULTS: condylar forces were found to consist of gravity forces due to the weight of the leg plus forces due to pretension in the collateral ligaments. The pretension force averaged 145 N but there was considerable variation because of ligament stiffness properties. Balancing from an imbalanced state could be achieved with adjustments within only 2° or 2 mm. CONCLUSION: The instrumented tibial trial provided force information which indicated which surgical correction options to carry out to achieve balancing. From an initial unbalanced state, relatively small changes could produce balancing, indicating the sensitivity of the procedure. CLINICAL RELEVANCE: Non-clinical. This study will assist in the balancing of the knee at total knee replacement surgery.

Identification of the landmark registration safe zones during total knee arthroplasty using an imageless navigation system.

Incorrect registration during computer assisted total knee arthroplasty (CA-TKA) leads to malposition of implants. Our aim was to evaluate the tolerable error in anatomic landmark registration. We incorrectly registered the femoral epicondyles, femoral and tibial centers, as well as the malleoli and documented the change in angulation or rotation. We found that the distal femoral epicondyles were the most difficult anatomic landmarks to register. The other bony landmarks were more forgiving. Identification of the distal femoral epicondyles has a high inter-observer and intra-observer variability. Our observation that there is less than 2mm of safe zone in the anterior or posterior direction during registration of the medial and lateral epicondyles may explain the inability of CA-TKA to improve upon the outcomes of conventional TKA.

Computer-assisted surgery patterns of ligamentous deformity of the knee: a clinical and cadaveric study.

Knee malalignment during total knee arthroplasty (TKA) is commonly classified as either varus or valgus on the basis of a standing anteroposterior radiograph. Computer-assisted surgery (CAS) navigation TKA provides precise dynamic evaluation of knee alignment throughout the full range of motion (FROM). The goal of this study was to classify patterns of CAS-generated knee deformity curves that match specific soft tissue contracture combinations. This can then be applied as an algorithm for soft tissue balancing on the basis of the preoperative knee deformity curve. Computer navigation-generated graphs from 65 consecutive TKA procedures performed by a single surgeon were analyzed. A stress-strain curve of the coronal alignment of the knee was recorded throughout FROM before bony resection. All graphs were classified into groups according to their pattern. Cadaveric knee models were then used to test the correlation between isolated and combined ligamentous contractures and identified CAS deformity curves. An analysis of the intraoperative knee alignment graphs revealed four distinct patterns of coronal deformity on the basis of intraoperative data: 13% diagonal, 18.5% C-shaped, 43.5% comma shaped, and 25% S-shaped. Each represents the change in varus and valgus alignment during FROM. All patterns were reproduced with cadaveric knees by recreating specific contracture constellations. A tight posterior capsule gave an S-shaped curve, a tight lateral collateral ligament gave a C-shaped curve, tight medial collateral ligament gave a diagonal curve, and a tight posterior lateral corner gave a comma-shaped curve. Release of the specific contractures resulted in correction of all patterns of deformity as measured by CAS. We propose a new classification system for coronal plane knee deformity throughout FROM. This system intends to match individual and combined soft tissue pathological contractures to specific stress-strain curves obtained through routine knee CAS preparation. This classification system may provide surgeons with a general guide for soft tissue balancing during computer-navigated TKA.

Total hip arthroplasty in above-knee amputees: a case report.

There are previous case reports in the literature that describe total knee and total hip arthroplasty (THA) in below-knee amputees, but we could find no case reports on above-knee amputees (AKAs) who have severe osteoarthritis of the hip. We present a case involving an AKA who developed severe osteoarthritis of the ipsilateral hip. Out patient underwent THA with a satisfactory postoperative outcome. Technical considerations for AKAs undergoing THA are also reviewed.

Effect of a perioperative intra-articular injection on pain control and early range of motion following bilateral TKA.

Pain control after total knee arthroplasty (TKA) is integral in the immediate postoperative period for early rehabilitation. Numerous different methods of postoperative analgesia are available, but each has its own risk of adverse side effects. This study was performed to prospectively evaluate the benefits of an intra-articular analgesic injection in patients undergoing bilateral TKA.Thirty consecutive patients undergoing bilateral TKA were enrolled in this prospective, randomized, controlled study. Each patient was randomized to receive (1) a perioperative intra-articular mixture of morphine, bupivacaine with epinephrine, and ketorolac in 1 knee, and (2) injectable sterile saline in the contralateral knee. Each patient acted as his or her own internal control. The pharmacologically injected knee had statistically significantly less pain immediately postoperatively when compared to the control knee and displayed significantly increased range of motion within the first week of rehabilitation.The use of an intraoperative intra-articular injection with the above drug combination significantly reduces patient pain and increases postoperative mobility with no apparent risks following bilateral TKA.

Massive wear and metallosis of an Acetabular Cup System presenting as pseudodislocation.

In primary and revision total hip arthroplasty (THA), the acetabular component continues to pose greater challenges than the femoral component. Numerous factors lead to polyethylene wear, which subsequently affects primary THA survival. Progressive polyethylene wear is associated with the occurrence of osteolysis, especially overlying the acetabulum, which can lead to component loosening and subsequent revision. Polyethylene failure usually manifests as massive liner wear up to the metal shell, fracture of the liner, or a combination of both. There is often a small amount of metallosis associated with this pathology. To our knowledge, massive wear of the acetabular metal shell, however, has not previously been reported in the literature. This article describes a case of massive wear through a polyethylene liner and the acetabular metal shell of an Acetabular Cup System (DePuy, Leeds, United Kingdom) that presented as an apparent dislocation 13 years following the index operation. The pseudodislocation was intraoperatively found to be penetration of the femoral head through the acetabular shell. The acetabular component was consequently revised to a larger cementless cup. The femoral component was mechanically stable and required no revision. Patients with long-standing Acetabular Cup System THA may experience acetabular metal shell wear-through phenomena presenting as a pseudodislocation, and this possibility should be taken into consideration during preoperative planning.

"Floating total knee": ipsilateral periprosthetic fractures of the distal femur and proximal tibia after total knee arthroplasty.

UNLABELLED: Currently, there are more than 300000 primary total knee arthroplasty (TKA) performed annually in the United States. It is estimated that 0.3% to 2.5% of these patients will sustain a periprosthetic fracture in association with a TKA [Haidukewych GJ, Jacofsky DJ, Hanssen AD. Treatment of periprosthetic fractures around a total knee arthroplasty. J Knee Surg 2003;16:111]. The first report of a periprosthetic fracture involving a TKA occurred in 1977 [Callaghan JJ. Periprosthetic fractures of the acetabulum during and following total hip arthroplasty. Instr Course Lect 1998;47:231]. The majority of periprosthetic fractures associated with a TKA are distal femoral fractures [Berry D. EPIDEMIOLOGY: hip and knee. In: Callaghan J, Duncan C, editors. Periprosthetic fractures after major joint replacement. Philadelphia: WB Saunders; 1999. p. 183]. Periprosthetic tibial fractures are rare and usually involve the medial tibial plateau in the presence of a loose component [Rand JA, Coventry MB. Stress fractures after total knee arthroplasty. J Bone Joint Surg Am 1980;62:226, Hanssen AD, Stuart MJ]. Treatment of periprosthetic tibial fractures. Clin Orthop 2000; p. 91]. The following case report describes the management of simultaneous ipsilateral distal femoral and proximal tibial periprosthetic fractures associated with a TKA. The patient was informed that data concerning the case would be submitted for publication. To our knowledge, this "floating total knee" injury has not been previously reported.

Musculoskeletal complications associated with lysosomal storage disorders: Gaucher disease and Hurler-Scheie syndrome (mucopolysaccharidosis type I).

PURPOSE OF REVIEW: Enzyme therapy for lysosomal storage disorders directed at correcting the underlying cause of disease represents the most significant recent advance in patient management. This review focuses on two disease groups: glycosphingolipidoses and mucopolysaccharidoses. Specifically, Gaucher disease and Hurler-Scheie syndrome have been selected as the prototypical disorder for each respective class. RECENT FINDINGS: Musculoskeletal complications are encountered in several of the lysosomal storage disorders and often represent a major source of extraneurologic morbidity, particularly in the subacute or chronic variants. Enzyme therapy has led to improvements in physical and functional well-being. However, bone involvement remains a recalcitrant feature, especially among patients with established disease before institution of therapy. SUMMARY: Early diagnosis and appropriate timely intervention are critical in achieving the best therapeutic results. A better understanding of the fundamental mechanisms of bone pathology may enable the identification of complementary approaches (eg, the use of bisphosphonates for severe osteopenia) for optimized outcomes. Symptomatic care and rigorous physical and occupational therapy remain critical components of a comprehensive management approach.