Jason E. Lang

Robotic systems in orthopaedic surgery

Robots have been used in surgery since the late 1980s. Orthopaedic surgery began to incorporate robotic technology in 1992, with the introduction of ROBODOC, for the planning and performance of total hip replacement. The use of robotic systems has subsequently increased, with promising short-term radiological outcomes when compared with traditional orthopaedic procedures. Robotic systems can be classified into two categories: autonomous and haptic (or surgeon-guided). Passive surgery systems, which represent a third type of technology, have also been adopted recently by orthopaedic surgeons. While autonomous systems have fallen out of favour, tactile systems with technological improvements have become widely used. Specifically, the use of tactile and passive robotic systems in unicompartmental knee replacement (UKR) has addressed some of the historical mechanisms of failure of non-robotic UKR. These systems assist with increasing the accuracy of the alignment of the components and produce more consistent ligament balance. Short-term improvements in clinical and radiological outcomes have increased the popularity of robot-assisted UKR. Robot-assisted orthopaedic surgery has the potential for improving surgical outcomes. We discuss the different types of robotic systems available for use in orthopaedics and consider the indication, contraindications and limitations of these technologies.

Achieving Accurate Ligament Balancing Using Robotic-Assisted Unicompartmental Knee Arthroplasty

Unicompartmental knee arthroplasty (UKA) allows replacement of a single compartment in patients with limited disease. However, UKA is technically challenging and relies on accurate component positioning and restoration of natural knee kinematics. This study examined the accuracy of dynamic, real-time ligament balancing using a robotic-assisted UKA system. Surgical data obtained from the computer system were prospectively collected from 51 patients (52 knees) undergoing robotic-assisted medial UKA by a single surgeon. Dynamic ligament balancing of the knee was obtained under valgus stress prior to component implantation and then compared to final ligament balance with the components in place. Ligament balancing was accurate up to 0.53 mm compared to the preoperative plan, with 83% of cases within 1 mm at 0°, 30°, 60°, 90°, and 110° of flexion. Ligamentous laxity of 1.31 ± 0.13 mm at 30° of flexion was corrected successfully to 0.78 ± 0.17 mm (P < 0.05). Robotic-assisted UKA allows accurate and precise reproduction of a surgical balance plan using dynamic, real-time soft-tissue balancing to help restore natural knee kinematics, potentially improving implant survival and functional outcomes.

Classic measures of hip dysplasia do not correlate with three-dimensional computer tomographic measures and indices

Acetabular dysplasia is a precursor to osteoarthritis of the hip, and it causes acute and degenerative injuries of soft tissue stabilisers. Traditional radiographic assessments of dysplasia are useful in moderate and severe dysplasia, but they have questionable reliability in mild dysplasia. Computed tomography (CT) reconstruction provides a method for calculation of acetabular geometry and analysis of existing radiographic methods. We performed a retrospective radiographic review of anteroposterior pelvic films and their corresponding pelvic CT scans. Using 30 skeletally mature patients, we analyzed the following five measurements for 60 hips: lateral centre edge angle of Wiberg (LCE), Tönnis angle, Sharp angle, a modified Sharp angle, and the depth to width acetabular index. We also estimated hip surface areas, volumes, and ratios from 3-D reconstructions of a CT scan taken within 60 days of the plain radiograph. The Pearson Correlation Coefficient was used to evaluate the relationship between the plain film measurements and the computed hip indices. No moderate or strong correlation was found between the measured plain film indices and the calculated hip indices. Traditional 2-D measurements used to define acetabular dysplasia have little to no ability to quantify hip volumes and surface areas. CT reconstruction provides a better screening tool in the identification of subtle acetabular hip dysplasia in adults. Level of Evidence: Level III

Magnitude of Limb Lengthening After Primary Total Knee Arthroplasty

Patients will often perceive a change in lower limb length after total knee arthroplasty (TKA). From this observed finding, we asked how frequently does a change in limb length occur after TKA. Preoperative and postoperative full-length standing radiographs were obtained for 102 knees in 98 patients who underwent TKA. Digital radiography software was used to measure the mechanical axis and limb length of the operative and nonoperative legs. Overall, 83% of the knees measured showed an increase in limb length after TKA. Preoperative varus alignment was associated with an average lengthening of 5.2 mm. Preoperative valgus alignment was associated with an average lengthening of 8.4 mm. Patients with a valgus deformity greater than 10° demonstrated the greatest average lengthening. It is the conclusion of this study that limb lengthening occurs frequently after TKA, back to a length similar to the nonoperative limb.

Patient Factors and Cost Associated with 90-Day Readmission Following Total Hip Arthroplasty.

This study sought to identify specific costs for 90-day readmissions following total hip arthroplasty in a bundled payment system. Hospital billing records revealed 139 readmissions (8.93%) in 1781 patients. Mean costs for surgical readmissions were greater (P=0.002) compared with medical reasons, but similar for Medicare/Medicaid and private payers (P=0.975). Costs for imaging, laboratory workup, medication and transfusions, and hospital cost correlated with increasing SOI (P<0.05). Patients transferred from outside hospitals or rehabilitation had higher hospital (P=0.006) and operating room costs (P=0.001) compared to patients admitted from ED or clinic. Hospitals that care for complex patients with Medicare/Medicaid may experience increased costs for unplanned 90-day readmissions highlighting considerations for payer mix.

Orthopedic resident work-shift analysis: are we making the best use of resident work hours?

BACKGROUND Surgery programs have been tasked to meet rising demands in patient surgical care while simultaneously providing adequate resident training in the midst of increasing resident work-hour restrictions. The purpose of this study was to quantify orthopedic surgery resident workflow and identify areas needing improved resident efficiency. We hypothesize that residents spend a disproportionate amount of time involved in activities that do not relate directly to patient care or maximize resident education. METHODS We observed 4 orthopedic surgery residents on the orthopedic consult service at a major tertiary care center for 72 consecutive hours (6 consecutive shifts). We collected minute-by-minute data using predefined work-task criteria: direct new patient contact, direct existing patient contact, communications with other providers, documentation/administrative time, transit time, and basic human needs. A seventh category comprised remaining less-productive work was termed as standby. RESULTS In a 720-minute shift, residents spent on an average: 191 minutes (26.5%) performing documentation/administrative duties, 167.0 minutes (23.2%) in direct contact with new patient consults, 129.6 minutes (17.1%) in communication with other providers regarding patients, 116.2 (16.1%) minutes in standby, 63.7 minutes (8.8%) in transit, 32.6 minutes (4.5%) with existing patients, and 20 minutes (2.7%) attending to basic human needs. Residents performed an additional 130 minutes of administrative work off duty. Secondary analysis revealed residents were more likely to perform administrative work rather than directly interact with existing patients (p = 0.006) or attend to basic human needs (p = 0.003). CONCLUSIONS Orthopedic surgery residents spend a large proportion of their time performing documentation/administrative-type work and their workday can be operationally optimized to minimize nonvalue-adding tasks. Formal workflow analysis may aid program directors in systematic process improvements to better align resident skills with tasks. LEVEL OF EVIDENCE III.

Tibial Component Alignment After Total Knee Arthroplasty with Intramedullary Instrumentation: A Prospective Analysis

The best operative technique for achieving appropriate postoperative alignment following total knee arthroplasty (TKA) remains controversial, with proponents of extramedullary, intramedullary and computer-assisted techniques. One hundred ninety-two consecutive patients undergoing TKA were prospectively evaluated with full-length lower extremity radiographs. Patients underwent cemented TKA using femoral and tibial intramedullary instrumentation. Digital radiographs were analyzed using PACS (AGFA Healthcare, Ridgefield Park, NJ) software. Tibial component alignment was measured in the coronal and sagittal planes. Tibial component slope averaged 3.89° + 1.96 for the cruciate-retaining components and averaged 1.7° + 1.92 for PS components. The average coronal tibial component alignment was 90.00°, and 99% were within 3° of neutral mechanical alignment with only 2 (1%) outliers. Intramedullary instrumentation resulted in excellent postoperative tibial component and lower extremity alignment.

Anterior intrapelvic migration of femoral trial head requiring secondary surgical approach for retrieval.

The current report describes a revision total hip arthroplasty in which the trial femoral head disassociated during reduction and migrated into a soft tissue capsule of the true pelvis between the external iliac vein and corona mortise. The authors believe this previously undescribed migration pattern was created by the patients history of recurrent dislocations. To retrieve the trial prosthesis without injuring the adjacent vasculature, a secondary surgical approach was utilized. The described case identifies the risk of pelvic migration in patients with a history of dislocations and reminds us that a secondary surgical approach should be considered to avoid devastating injury to the neighboring vasculature.

Skin avulsion injuries with use of adhesive surgical drapes.

Iodophor-impregnated adhesive drapes are commonly used to reduce the incidence of surgical site infections (SSI).While proper and discretionary use of drapes can provide significant benefit, there are potential risks. We present two cases of degloving injuries sustained from use of these drapes during total knee arthroplasty. The patients, deemed high risk for potential skin avulsion injuries, received standard wound care and close follow-up which resulted in healing of the lesions at 6-week follow-up.

Quantifying the force transmission through the pelvic joints during total hip arthroplasty: A pilot cadaveric study

Background: Total hip arthroplasty is one of the most successful and cost effective procedures in orthopedics. The purpose of this study is to investigate force transmission through the sacroiliac joint as a possible source of post‐operative pain after total hip arthroplasty through the following three questions: Does the ipsilateral sacroiliac joint, contralateral sacroiliac joint, or pubic symphysis experience more force during placement? Does the larger mallet used to seat the implant generate a higher force? Does the specimens bone density or BMI alter force transmission? Methods: A solid design acetabular component was impacted into five human cadaver pelves with intact soft tissues. The pressure at both sacroiliac joints and the pubic symphysis was measured during cup placement. This same procedure was replicated using an existing pelvis finite element model to use for comparison. Findings: The location of the peak force for each hammer strike was found to be specimen specific. The finite model results indicated the ipsilateral sacroiliac joint had the highest pressure and strain followed by the pubic symphysis over the course of the full simulation. The heft of the mallet and bone mineral density did not predict force values or locations. The largest median force was generated in extremely obese specimens. Interpretation: Contrary to previous ideas, it is highly unlikely that forces experienced at the pelvic joints are large enough to contribute post‐operative pain during impaction of an acetabular component. These results indicate more force is conveyed to the pubic symphysis compared to the sacroiliac joints. HighlightsThe ipsilateral sacroiliac joint sustained more force than the contralateral joint.The pubic symphysis experienced more force overall during impaction.The location of the peak force for each hammer strike is specimen specific.The mass of the mallet did not predict force values or locations.Bone mineral density did not correlate to peak force measured at the joints.