Imageless Computer Navigation Reduces 5-Year All-Cause Revision Rates After Primary Total Knee Arthroplasty.

BACKGROUND: The use of surgical navigation has been shown to reduce revision rates after total knee arthroplasty (TKA) in patients <65 years of age. It is unknown if this benefit extends to older patients. We hypothesized that the use of surgical navigation would reduce rates of all-cause revision in patients of all ages. METHODS: In this cohort study, we queried the Truven MarketScan all-payer database to identify patients who underwent TKA from 2007 to 2015. Current Procedural Terminology codes were used to create 2 groups based on whether intraoperative navigation was used. Demographics, comorbidities, complications, and revision rates were determined. International Classification of Diseases codes were used to determine reasons for revision. RESULTS: The conventional TKA cohort included 312,173 patients. The navigation cohort included 20,881 patients. There were not any clinically significant differences in demographics between the cohorts. All-cause revision rates were lower in the navigation cohort at 1 year (0.4% vs 0.5%, P = .04), 2 years (0.7% vs 0.9%, P = .003), and 5 years (0.9% vs 1.3%, P < .001) of follow-up. Revisions for mechanical loosening were more common in the conventional cohort (30.8% vs 21.9%, P = .009). Rates of revision for other causes, including infection, did not differ between groups, with the numbers available. CONCLUSION: The use of surgical navigation yielded a 30.7% reduction in the all-cause revision rate at 5-year follow-up compared to conventional TKA. This benefit increased as follow-up duration increased. Increased usage of this inexpensive technology, from the current 6.3% in this US cohort, may reduce healthcare costs. LEVEL OF EVIDENCE: III.

Unipedal balance is affected by lower extremity joint arthroplasty procedure 1 year following surgery.

Lower Extremity Joint Arthroplasty (LEJA) surgery is an effective way to alleviate painful osteoarthritis. Unfortunately, these surgeries do not normalize the loading asymmetry during the single leg stance phase of gait. Therefore, we examined single leg balance in 234 TJA patients (75 hips, 65 knees, 94 ankles) approximately 12 months following surgery. Patients passed if they maintained single leg balance for 10s with their eyes open. Patients one year following total hip arthroplasty (THA-63%) and total knee arthroplasty (TKA-69%) had similar pass rates compared to a total ankle arthroplasty (TAA-9%). Patients following THA and TKA exhibit better unilateral balance in comparison with TAA patients. It may be beneficial to include a rigorous proprioception and balance training program in TAA patients to optimize functional outcomes.

Percent body fat more associated with perioperative risks after total joint arthroplasty than body mass index.

Understanding the impact of obesity on elective total joint arthroplasty (TJA) remains critical. Perioperative outcomes were reviewed in 316 patients undergoing primary TJA. Higher percent body fat (PBF) was associated with postoperative blood transfusion, increased hospital length of stay (LOS) >3 days, and discharge to an extended care facility while no significant differences existed for BMI. Additionally, PBF of 43.5 was associated with a 2.4× greater likelihood of blood transfusion, PBF of 36.5 with a 1.9× greater likelihood for LOS >3 days, and PBF of 36.0 with a 1.4× greater likelihood for discharge to an extended care facility. PBF may be a more effective measure than BMI to use in screening for perioperative risks and acute outcomes associated with obese total joint patients.

Effect of acetabular labrum tears on hip stability and labral strain in a joint compression model.

BACKGROUND: Acetabular labrum tears are now commonly diagnosed in young and active patients. Because the role of the acetabular labrum is incompletely understood, it is critical to determine how these tears affect native hip biomechanics. HYPOTHESIS: Radial and circumferential labral tears significantly decrease hip stability and significantly alter strain patterns in the anterior and anterior-superior acetabular labrum. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-two human cadaveric hips without evidence of degeneration or dysplasia were assigned to a circumferential tear (n = 11) and a radial tear (n = 11) group. The hips were tested in a neutral position with an average compressive force of 25 N. In the circumferential tear group, the labral states were intact; 1-, 2-, and 3-cm circumferential tears; a 3-cm partial labrectomy; and a full labrectomy. In the radial tear group, the labral states were intact; a radial tear; a 1-, 2-, and 3-cm partial labrectomy; and a full labrectomy. The effect of labral injury on the stability ratio (peak dislocation force/compressive loads) and labral strain in the anterior and anterior-superior labrum was analyzed using repeated-measures analysis of variance. RESULTS: There was no significant difference in stability ratio after circumferential tears 3 cm or less in size compared with the intact labral state. Strain in the anterior and anterior-superior labrum was either unchanged or increased after circumferential labral tear. There was no significant difference in stability ratio after a radial tear or a 1-cm partial labrectomy compared with the intact labral state. A 2-cm partial labrectomy significantly decreased the stability ratio. Anterior and anterior-superior labral strain significantly decreased after a radial tear. CONCLUSION: Under the influence of joint compression in a neutral hip position, the acetabular labrum continues to resist femoral head dislocation despite detachment from the acetabular rim. A radial tear in the acetabular labrum decreases adjacent labral strain, but removal of 2 cm or more of the acetabular labrum is needed before hip stability decreases. CLINICAL RELEVANCE: The findings suggest that the acetabular labrum continues to function to resist femoral head translation despite chondral-labral separation and that labral preservation, particularly with larger tears, may be important for maintaining hip stability. Further studies are needed to determine the effect of partial labral excision on the stability ratio with the hip in provocative positions such as extension, external rotation, and abduction.

Effect of ankle flexion angle on axial alignment of total ankle replacement.

BACKGROUND: The Salto Talaris Anatomic® (Tornier) total ankle replacement (TAR) has found widespread use in the United States and features rotationally mobile trial components that auto-align the final components, which themselves are rotationally fixed and highly congruent. Based on recent work on prosthetic and native ankle kinematics, we investigated the influence of the ankle flexion angle at the time of final component preparation on the axial alignment of the Salto Talaris TAR. MATERIALS AND METHODS: Following a power analysis based on a clinically meaningful difference of five degrees, eight fresh-frozen cadaveric thigh-to-foot specimens underwent installation of trial components using the Salto Talaris TAR system. Specimens were cycled from maximal dorsiflexion (DF) to plantarflexion (PF), as called for in the surgical technique guide, and drilling for the final component was carried out in both five degrees of DF and 15 degrees of PF using separate drill holes. These were compared with a reference drill hole previously placed along the axis of distal tibial cutting guide. Data were analyzed to determine whether components prepared in DF differed from those prepared in PF with respect to median (and variance) rotation. RESULTS: We found no significant difference in median axial alignment (p = 0.139) or in variances between the two groups (p=0.937). CONCLUSION: The ankle flexion angle at the time of final component preparation did not significantly alter the axial alignment of the Salto Talaris TAR. CLINICAL RELEVANCE: Therefore, the rotational alignment of the tibial component is determined by the tibial bone cuts and will not auto-align to the rotation of the talar component.

Novel reconstruction of a static medial ligamentous complex in a flatfoot model.

BACKGROUND: Little progress has been made addressing reconstruction of the static medial ligamentous structures of the foot. The purpose of this investigation was to reconstruct a flatfoot deformity with a novel static medial ligamentous complex (MLC) and evaluate its ability to correct talar head subluxation and radiographic deformity in a cadaveric model. MATERIALS AND METHODS: Eight fresh frozen cadaveric specimens underwent cyclic preconditioning and static axial loading. Loading was applied to the intact foot, the severe flatfoot, and the reconstructed MLC foot. Anteroposterior (AP) and lateral radiographs were taken at each stage. The talo-first metatarsal angle, medial cuneiform height, talocalcaneal angle, and the calcaneal pitch angle were measured on the lateral views and the talo-first metatarsal angle was measured on the anteroposterior views. RESULTS: Compared with the intact foot, the flatfoot showed significant change in the AP talo-first metatarsal angle (p = 0.001), the lateral talo-first metatarsal angle (p = 0.002), the medial cuneiform height (p = 0.007), the talocalcaneal angle (p = 0.03), and the calcaneal pitch angle (p = 0.018). After MLC reconstruction, there was a significant change in the AP talo-first metatarsal angle (p = 0.001), the lateral talo-first metatarsal angle (p = 0.002), and the medial cuneiform height (p = 0.007) and these values were not significantly different than the intact foot. The talocalcaneal angle and the calcaneal pitch angle remained significantly undercorrected after static MLC reconstruction. CONCLUSION: Static MLC reconstruction was effective in correcting several key radiographic parameters in a cadaveric flatfoot model. CLINICAL RELEVANCE: The surgical technique evaluated here may be useful as a new soft tissue reconstructive procedure for treating adult flatfoot.

Biomechanical comparison of figure-of-8 versus cylindrical tibial inlay constructs for arthroscopic posterior cruciate ligament reconstruction.

PURPOSE: To determine the biomechanical strength of Achilles tendon allografts with 2 different bone plug configurations as prepared for arthroscopic posterior cruciate ligament reconstruction when fixed as tibial inlay constructs. METHODS: Nine matched pairs of cadaveric tibias were reconstructed by a standardized tibial inlay technique by use of either a cylindrical bone plug (12 mm in diameter) or a figure-of-8 bone plug (12 x 18 mm). Constructs were subjected to cyclic tensile loading followed by load to failure. The statistical analysis consisted of paired t tests with significance set at P < .05. RESULTS: No significant differences were found in yield load, ultimate load, stiffness, load at 5 mm, and total cyclic displacement between the groups. Although both constructs showed equivalent biomechanical properties, the tendons of the cylindrical bone plugs failed predominantly by shear off the bone compared with the figure-of-8 plugs, which failed by the sutures tearing through the tibial plateau. CONCLUSIONS: Tibial constructs with cylindrical and figure-of-8 bone plugs as prepared for use in arthroscopic posterior cruciate ligament reconstruction have comparable immediate biomechanical stability when fixed by a tibial inlay technique in a cadaveric model. CLINICAL RELEVANCE: Cylindrical and figure-of-8 bone plugs have comparable immediate biomechanical stability when fixed by a tibial inlay method, with the cylindrical technique being potentially technically easier to perform.

Activation of the shoulder musculature during pendulum exercises and light activities.

STUDY DESIGN: Prospective, single-group, repeated-measures design. OBJECTIVES: To evaluate electromyographic (EMG) signal amplitude in the supraspinatus, infraspinatus, and deltoid muscles during pendulum exercises and light activities in a group of healthy subjects. BACKGROUND: There are numerous rehabilitation protocols used after rotator cuff repair. One of the most commonly used exercises in these protocols is the pendulum. Patients can easily perform these exercises incorrectly, and may also perform light activities of daily living without knowing that they may be putting excessive stress on the repair. The effect of improperly performed pendulum exercises and light activities after rotator cuff repair is unknown. METHODS: Muscle activity was recorded in 13 subjects performing pendulum exercises incorrectly and correctly in both large (51-cm) and small (20-cm) diameters, and while typing, drinking, and brushing their teeth. RESULTS: Incorrect and correct large pendulums and drinking elicited more than 15% maximum voluntary isometric contraction in the supraspinatus and infraspinatus. The supraspinatus EMG signal amplitude was greater during large, incorrectly performed pendulums than during those performed correctly. Both correct and incorrect large pendulums resulted in statistically higher muscle activity in the supraspinatus than the small pendulums. CONCLUSION: Larger pendulums may require more force than is desirable early in rehabilitation after rotator cuff repair.

Defining safe rehabilitation for ulnar collateral ligament reconstruction of the elbow: a biomechanical study.

BACKGROUND: Ulnar collateral ligament reconstruction of the elbow using a variety of techniques has been successful in enabling overhead athletes with ulnar collateral ligament insufficiency to return to competition. Most current postoperative rehabilitation programs begin with a period of motion restriction, including limiting elbow extension, that is followed by a transition from elbow strengthening to an interval throwing program, to competition. Motion restrictions early in the postoperative period may increase the risk for contractures. There is limited information to support current motion restrictions. PURPOSE: (1) To determine strain on the reconstructed ulnar collateral ligament during a rehabilitation protocol that includes passive range of motion, isometric muscle contraction, and varus and valgus torques. (2) To develop guidelines for a safe initial rehabilitation protocol. STUDY DESIGN: Controlled laboratory study. METHODS: Eight cadaveric elbows underwent ulnar collateral ligament reconstruction with the docking technique using a gracilis tendon graft. Differential variable reluctance transducers on the anterior and posterior bands of the reconstructed anterior bundle of the ulnar collateral ligament were used to measure strain, while an optical motion tracking system monitored elbow motion. Strain was measured in the following 3 settings: passive range of motion, 22.2 N isometric flexion and extension contractions, and 3.34 N x m varus and valgus torques with the arm at 90 degrees of flexion. RESULTS: Range of motion from maximum extension to 50 degrees of flexion produced 3% or less strain in both bands of the reconstructed ligament. Forearm rotation did not significantly affect strain in the anterior or posterior bands (P = .336 and P = .357). Strain at 90 degrees approached 7% in the posterior band (upper 95% confidence interval). Isometric muscle contractions had no measurable effect on strain. Varus torques decreased and valgus torques increased strain significantly (P < .05). CONCLUSION: In the immediate postoperative period, full extension is safe, while flexion beyond 50 degrees may place deleterious strain on the reconstruction. Isometric flexion and extension exercises do not increase ligament strain but may be unsafe at 90 degrees of flexion, while valgus exercises (internal rotation at the shoulder) can increase strain in the reconstructed ligament. CLINICAL RELEVANCE: The results have implications for the development of appropriate rehabilitation protocols after ulnar collateral ligament reconstructive surgery.