Early and mid-range followup studies of shoulder arthroplasty have been encouraging, showing good and excellent results in > 90% of shoulders. Despite this success, complications in shoulder replacement surgery are inevitable, with an incidence of approximately 14%. Numerous complications have been identified and include the following factors in order of decreasing frequency: instability, rotator cuff tear, ectopic ossification, glenoid component loosening, intraoperative fracture, nerve injury, infection, and humeral component loosening. Successful treatment of these difficulties requires careful identification and subsequent analysis of all factors contributing to the complication, knowing that the etiology is often multifactorial. Failed shoulder arthroplasty can be successfully managed with revision surgery, but the technically challenging surgery and the overall results are inferior compared with other diagnostic categories.

Complications of shoulder arthroplasty

Background: Coronal malalignment occurs frequently in total knee arthroplasty (TKA) and reduces implant longevity and function. Designed to improve consistency and efficiency, patient- specific positioning guides (PSPG) generated from preoperative imaging studies represent a paradigm shift from manual instrumentation (MI) and intraoperative computer navigation. Purposes: We compare the efficacy of PSPG to MI in (1) restoring mechanical axis of the extremity and (2) achieving neutral alignment of the femoral and tibial components. Methods: We retrospectively examined 696 postoperative anteroposterior standing long-leg radiographs after TKA (545 PSPG, 151 MI) by two surgeons. Coronal alignment was assessed by determining the zone in which the overall mechanical axis (OMA) passed through the knee, measuring the hip-knee-ankle (HKA) angle between the tibial and femoral mechanical axes, and finally, noting the alignment of the femoral and tibial components with respect to their mechanical axes. Results: The OMA passed through the central third more frequently with PSPG than MI for both surgeons (JHD: 86.6% vs. 77%, p = 0.02; AVL: 86.4% vs. 74.5%, p = 0.11). For the senior author, while percent of HKA outliers >3i,° was similar between PSPG and MI, the mean error from neutral for these patients was significantly less with PSPG than MI (4.50i,° vs. 5.25i,°, p = 0.0031). The tibial component demonstrated no significant difference between PSPG and MI. With PSPG, average individual deviation from neutral for the femoral component was significantly less (0.91i,° vs. 1.34i,°, p = 0.0005) and had fewer outliers >2i,° (4.9% vs. 19.6%, p = 0.017). Discussion: Improved coronal alignment in total knee arthroplasty (TKA) is associated with greater patient satisfaction, better functional scores and increased implant longevity [11,30,31,36]. Recently, preoperative three-dimensional imaging and custom manufacturing have enabled the development of patient-specific positioning guides (PSPG). Designed to improve consistency and efficiency, PSPG represents a paradigm shift away from intramedullary and extramedullary guides, or manual instrumentation (MI), and an evolution from intraoperative computer-assisted navigation (CAN). Even in the hands of experienced surgeons, MI frequently results in significant component angulation and mechanical axis malalignment [32]. Multiple studies support the restoration of a neutral axis as a critical factor in implant performance and potential longevity of total knee arthroplasty [2, 3, 5, 18, 41, 44]. Intraoperative CAN has been shown to improve precision and accuracy of alignment compared to MI with a reduction in the number of outliers (less than 3i,° varus/valgus) [32, 38] and the amount of blood loss [39], but is hindered by time-consuming landmark registration, increased operative length [7], greater cost, the risk for stress fracture, pin loosening, and a substantial learning curve [6, 22, 29, 43]. Patient-specific positioning guides, on the other hand, purportedly eliminate many of the disadvantages of CAN while still allowing the bone resections to match the measured overall mechanical axis. While accurate and precise alignment guides are potent tools in restoring the proper overall mechanical axis, they are not a substitute for careful preoperative planning, good clinical and intraoperative judgment, appropriate soft tissue balancing, and precise implantation technique. Nevertheless, patient-specific positioning guides can provide the first step in the right direction to a successful TKA. Conclusions: Patient-specific positioning guides can assist in restoration of the mechanical axis with reduction in outliers. Level of Evidence: Level III, retrospective case-control study

Improved Accuracy of Alignment With Patient-Specific Positioning Guides Compared with Manual Instrumentation in TKA

In 2006, we reviewed articles published between 1996 and 2005 pertaining to anatomic total shoulder arthroplasty (TSA); that analysis revealed 414 complication events after 2,810 total shoulder replacements (a rate of 14.7%)[1][1]. Component loosening accounted for 161 (39%) of the 414 complications

Complications of Shoulder Arthroplasty.

The aim of this prospective multicentre study was to report the patient satisfaction after total knee replacement (TKR), undertaken with the aid of intra-operative sensors, and to compare these results with previous studies. A total of 135 patients undergoing TKR were included in the study. The soft-tissue balance of each TKR was quantified intra-operatively by the sensor, and 18 (13%) were found to be unbalanced. A total of 113 patients (96.7%) in the balanced group and 15 (82.1%) in the unbalanced group were satisfied or very satisfied one year post-operatively (p = 0.043). A review of the literature identified no previous study with a mean level of satisfaction that was greater than the reported level of satisfaction of the balanced TKR group in this study. Ensuring soft-tissue balance by using intra-operative sensors during TKR may improve satisfaction.

https://static.prod.orthosensor.com/wp-content/uploads/2015/04/04-Increased-Satisfaction-After-TKA.pdf

Increased satisfaction after total knee replacement using sensor-guided technology

Recently, there is a growing interest in surgical variables that are intraoperatively controlled by orthopaedic surgeons, including lower leg alignment, component positioning and soft tissues balancing. Since more tight control over these factors is associated with improved outcomes of unicompartmental knee arthroplasty and total knee arthroplasty (TKA), several computer navigation and robotic-assisted systems have been developed. Although mechanical axis accuracy and component positioning have been shown to improve with computer navigation, no superiority in functional outcomes has yet been shown. This could be explained by the fact that many differences exist between the number and type of surgical variables these systems control. Most systems control lower leg alignment and component positioning, while some in addition control soft tissue balancing. Finally, robotic-assisted systems have the additional advantage of improving surgical precision. A systematic search in PubMed, Embase and Cochrane Library resulted in 40 comparative studies and three registries on computer navigation reporting outcomes of 474,197 patients, and 21 basic science and clinical studies on robotic-assisted knee arthroplasty. Twenty-eight of these comparative computer navigation studies reported Knee Society Total scores in 3504 patients. Stratifying by type of surgical variables, no significant differences were noted in outcomes between surgery with computer-navigated TKA controlling for alignment and component positioning versus conventional TKA (p = 0.63). However, significantly better outcomes were noted following computer-navigated TKA that also controlled for soft tissue balancing versus conventional TKA (mean difference 4.84, 95 % Confidence Interval 1.61, 8.07, p = 0.003). A literature review of robotic systems showed that these systems can, similarly to computer navigation, reliably improve lower leg alignment, component positioning and soft tissues balancing. Furthermore, two studies comparing robotic-assisted with computer-navigated surgery reported superiority of robotic-assisted surgery in controlling these factors. Manually controlling all these surgical variables can be difficult for the orthopaedic surgeon. Findings in this study suggest that computer navigation or robotic assistance may help managing these multiple variables and could improve outcomes. Future studies assessing the role of soft tissue balancing in knee arthroplasty and long-term follow-up studies assessing the role of computer-navigated and robotic-assisted knee arthroplasty are needed.

Current state of computer navigation and robotics in unicompartmental and total knee arthroplasty: a systematic review with meta-analysis.

Recently, technological advances have made it possible to quantify pounds of pressure across the bearing surface during TKA. This multicenter evaluation, using intraoperative sensors, was performed for two reasons: 1) to define "balance" 2) to determine if patients with balanced knees exhibit improved short-term clinical outcomes. Outcomes scores were compared between "balanced" and "unbalanced" patients. At 6-months, the balanced cohort scored 172.4 and 14.5 in KSS and WOMAC, respectively; the unbalanced cohort scored 145.3 and 23.8 in KSS and WOMAC (P < 0.001). Out of all confounding variables, balanced joints were the most significant contributing factor to improved postoperative outcomes (P < 0.001). Odds ratios demonstrate that balanced joints are 2.5, 1.3, and 1.8 times more likely to achieve meaningful improvement in KSS, WOMAC, and activity level, respectively.

https://static.prod.orthosensor.com/wp-content/uploads/2014/01/JOA-Article-A-New-Method-for-Defining-Balance.pdf

A new method for defining balance: promising short-term clinical outcomes of sensor-guided TKA.

Background: Acromial fractures following reverse shoulder arthroplasty are difficult to identify and have variable effects onoutcomes. A reproducible classification system is needed to categorizethese fractures before it is possible to evaluate optimal treatment. The purposes of this study were to investigate the ability of radiographs to detect acromial fractures and establish fracture union, and to assess the reliability of a new classification system of postoperative acromial fractures based on the involvement of the deltoid origin. Methods: Eighteen patients presenting with pain along the acromion or scapular spine following reverse shoulder arthroplasty were evaluated for acromial fractures over a period of fifty-six months. If radiographic findings were negative, computed tomography (CT) scans were performed. Sixteen acromial fractures were identified and classified into subtypes on the basis of the deltoid muscle origin: type I indicated involvement of a portion of the anterior and middle deltoid origin; type II,at leastthe entire middledeltoid originwith a portionbut notallof the posterior deltoidorigin; andtype III, theentire middle and posterior deltoid origin. The average age of the patients at the time of surgery was seventy-seven years (range, fifty-seven to eighty-seven years); the average duration of follow-up after surgery was twenty-five months (range, seven to forty-eight months). All fractures were treated nonoperatively. Blinded, fellowship-trained shoulder surgeons reviewed images that best illustrated the fracture, and the interobserver reliability of the classification system was evaluated. The reliabilityofradiographstodetectthefractureatthetimeoftheinitialpresentationofpainandtoobserveultimatefracture union was evaluated. Results: Interobserver reliability of the classification system was excellent (interclass correlation coefficient of 0.96). Radiographs were unreliable at detecting acromialfractures at thetime of the initial presentation of pain (k= 20.5) and at determining fracture union (k = 0.05). Conclusions: Radiographs may be unreliable for detecting acromial fractures after reverse total shoulder arthroplasty, and CT scans are often needed to identify the fracture. Once identified, postoperative acromial fractures can be reliably classified into three subtypes. Nonoperative treatment of postoperative acromial fractures results in limitation of functional outcomes. Level of Evidence: Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Classification of postoperative acromial fractures following reverse shoulder arthroplasty.

Although total knee arthroplasty has a high success rate, poor outcomes and early revision are associated with ligament imbalance. This multicenter evaluation was performed in order to provide 1-year followup of a previously reported group of patients who had sensor-assisted TKA, comparing the clinical outcomes of quantitatively balanced versus unbalanced patients. At 1 year, the balanced cohort scored 179.3 and 10.4 in KSS and WOMAC, respectively; the unbalanced cohort scored 156.1 and 17.9 in KSS and WOMAC (P < 0.001; P = 0.085). The average activity level scores of quantitatively balanced patients were 68.6 (corresponding to tennis, light jogging, and heavy yard work), while the average activity level of unbalanced patients was 46.7 (corresponding to light housework, and limited walking distances) (P = 0.015). Out of all confounding variables, a balanced articulation was the most significant contributing factor to improved postoperative outcomes (P < 0.001).

/pdf/primary-tka-patients-with-quantifiably-balanced-soft-tissue-3natvibboq.pdf

Primary TKA Patients with Quantifiably Balanced Soft-Tissue Achieve Significant Clinical Gains Sooner than Unbalanced Patients.

Background Currently, soft-tissue imbalance contributes to several of the foremost reasons for revision following primary TKA, including instability, stiffness, and aseptic loosening. In order to decrease the incidence of soft-tissue imbalance, intraoperative sensors were developed to provide real-time, quantitative load data within the knee. This study examines the intraoperative data of a group of multicenter patients to determine how targeted ligament releases affect intra-articular loading, and to understand which types of releases are necessary to achieve quantified ligament balance. Methods A group of 129 patients received sensor-assisted TKA, as part of a multicenter study. Medial and lateral loading data were collected pre-release, during any sequential releases, and post-release. All data were collected at 10°, 45°, and 90° during range of motion testing. Ligament release type, release technique type, and resultant loading were collected. Results Loading across the joint decreased, overall, and became more symmetrical after releases were performed. On average, between 2 and 3 corrections were made (up to 8) in order to achieve ligament balance. The ligament release type and subsequent quantified change in loading were in agreement with historical, qualified sources. Conclusion Objective data from sensor output may assist surgeons in decreasing loading variability and, thereby, decreasing ligament imbalance and its associated complications.

C Anderson

Papers

A new method for defining balance: promising short-term clinical outcomes of sensor-guided TKA.

Classification of postoperative acromial fractures following reverse shoulder arthroplasty.

Increased satisfaction after total knee replacement using sensor-guided technology

Primary TKA Patients with Quantifiably Balanced Soft-Tissue Achieve Significant Clinical Gains Sooner than Unbalanced Patients.

A Targeted Approach to Ligament Balancing Using Kinetic Sensors