[Total knee arthroplasty. Patient-specific instruments and implants]

Patient specific implants versus conventional implants in primary total knee arthroplasty: No significant difference in patient reported outcomes at 5 years

Background

Patient specific implants (PSI) represent a novel innovation aimed to improve patient satisfaction and function after total knee arthroplasty (TKA); however, longitudinal patient reported outcome measures (PROMs) for PSI are not well described. We sought to primarily evaluate PROMs of patients undergoing TKA with either PSI or off-the-shelf (OTS) implants at mid-term follow-up.

Methods

A retrospective review was performed on a prospectively collected cohort of 43 primary, cruciate-retaining TKAs performed with PSI (n = 23) and OTS implants (n = 20) by a single surgeon. Patient demographics, operative characteristics, range of motion (ROM) return, reoperations, and outcomes [Patient-Reported Outcomes Measurement Information System (PROMIS) T-score, Knee Injury and Osteoarthritis outcome score (KOOS), and Knee Society Score-Function (KSS-F)] were compared. Mean follow-up was 5 years.

Results

TKA performed with either PSI and OTS implants demonstrated no difference in obtaining ROM by 3 months (extension 3° short of full extension vs. 0°, p = 0.16) or flexion (114° vs. 115°, p = 0.99) and final ROM was identical [0° extension to 120° flexion (p = 1)]. Although not significant (p = 0.42), 5 (22%) PSI TKA and 2 (10%) OTS implant patients required manipulation under anesthesia. KSS-F and PROMIS T-scores were higher in the PSI versus OTS TKA patients, respectively (90 vs. 73, p = 0.002; 51.6 vs. 44.5, p = 0.01). However, after multivariable analysis, none of these continuous outcome measures were significantly different (p = 0.28 for KSS and p = 0.45 for PROMIS T-score) between the groups.

Conclusion

In a series of TKAs performed with PSI, no difference existed in postoperative ROM, reoperations, or patient-reported outcomes compared to OTS implants at 5 years. Surgeons may utilize the equivocal midterm results during TKA preoperative patient discussion of implant technologies.

The Impact of Total Knee Replacement with a Customized Cruciate-Retaining Implant Design on Patient-Reported and Functional Outcomes

Purpose: To treat patients with tricompartimental knee osteoarthritis (OA), a customized cruciate-retaining total knee arthroplasty (CCR-TKA) system can be used, including both individualized instrumentation and implants. The objective of this monocentric cohort study was to analyze patient-reported and functional outcomes in a series of patients implanted with the second generation of this customized implant. Methods: At our arthroplasty center, we prospectively recruited a cohort of patients with tricompartmental gonarthrosis to be treated with total knee replacement (TKA) using a customized cruciate-retaining (CCR) implant design. Inclusion criteria for patients comprised the presence of intact posterior cruciate and collateral ligaments and a knee deformity that was restricted to <15° varus, valgus, or flexion contracture. Patients were assessed for their range of motion (ROM), Knee Society Score (KSS), Western Ontario and McMaster University osteoarthritis index (WOMAC), and short form (SF)-12 physical and mental scores, preoperatively, at 3 and 6 months, as well as at 1, 2, 3, and 5 years of follow-up (FU) postoperatively. Results: The average age of the patient population was 64 years (range: 40–81), the average BMI was 31 (range: 23–42), and in total, 28 female and 45 male patients were included. Implant survivorship was 97.5% (one septic loosening) at an average follow-up of 2.5 years. The KSS knee and function scores improved significantly (p < 0.001) from, respectively, 41 and 53 at the pre-operative visit, to 92 and 86, respectively, at the 5-year post-operative time point. The SF-12 Physical and Mental scores significantly (p < 0.001) improved from the pre-operative values of 28 and 50, to 50 and 53 at the 5-year FU, respectively. Patients experienced significant improvements in their overall knee range of motion, from 106° at the preoperative visit to 122°, on average, 5 years postoperatively. The total WOMAC score significantly (p < 0.001) improved from 49.1 preoperatively to 11.4 postoperatively at 5-year FU. Conclusions: Although there was no comparison to other implants within this study, patients reported high overall satisfaction and improvement in functional outcomes within the first year from surgery, which continued over the following years. These mid-term results are excellent compared with those reported in the current literature. Comparative long-term studies with this device are needed. Level of evidence 3b (individual case–control study).

Single Use Instruments for Implanting a Contemporary Total Knee Arthroplasty System Are Accurate, Efficient, and Safe

BACKGROUND

Single use instruments (SUI) is a potential mechanism to improve efficiency and reduce cost in total knee arthroplasty (TKA). New technology requires patient safety and surgical accuracy. A multi-center study of SUI vs reusable mechanical instrumentation (RUI) for a TKA system compared implant placement accuracy and operating room (OR) efficiency.

METHODS

Four surgeons implanted 88 primary TKAs, N = 44 RUI and N = 44 SUI. Accuracy was measured radiographically at 3 months. The primary endpoint was non-inferiority of absolute value of mechanical axis alignment. Radiographic endpoints, OR times, and adverse events were also evaluated.

RESULTS

Seventy-five subjects completed the study (41 SUI/34 RUI). The primary endpoint non-inferiority of SUI vs RUI was met, with no significant difference between SUI and RUI in most radiographic parameters (distal femoral varus-valgus, proximal tibial varus-valgus, tibial slope, or subjects within 3° of target); there was a slight difference in femoral component flexion angle (P = .015). SUI and RUI mean (SD) OR set-up times were 18.8 (10.03) and 26.7 (6.93) (P <.001), and surgical times (first incision to last stitch) were 64.6 (16.95) and 60.5 (19.01) (P = .295), respectively. Differences in OR clean-down and anesthesia were not significant. There were no revisions, and there was no significant difference in the number of reported adverse events.

CONCLUSION

SUI resulted in similar accuracy of implant placement to RUI with decreased OR set-up time and no increase in adverse events. These results support the safety and efficacy of SUI for performing TKA. Further analysis of potential economic and technical advantages is warranted.

Patient-specific cruciate-retaining total knee replacement with individualized implants and instruments (iTotal™ CR G2)

OBJECTIVE

Treatment of tricompartimental osteoarthritis (OA) using customized instruments and implants for cruciate-retaining total knee arthroplasty. Use of patient-specific instruments and implants (ConforMIS iTotal^TM CR G2) together with a 3D-planning protocol (iView®). Retropatellar resurfacing is optional.

INDICATIONS

Symptomatic tricompartmental OA of the knee (Kellgren-Lawrence stage IV) with preserved posterior cruciate ligament (PCL) after unsuccessful conservative or joint-preserving surgical treatment.

CONTRAINDICATIONS

Knee ligament instabilities of the posterior cruciate or collateral ligaments. Infection. Relative contraindication: knee deformities >15° (varus, valgus, flexion); prior partial knee replacement.

SURGICAL TECHNIQUE

Midline or parapatellar medial skin incision, medial arthrotomy; distal femoral resection with patient-specific cutting block; tibial resection using either a cutting jig for the anatomic slope or a fixed 5° slope. Balancing the knee in extension and flexion gap using patient-specific spacer. The final tibial preparation achieved with gap-balanced placement of the femoral cutting jigs. Kinematic testing using anatomic trial components. Final implant components are cemented in extension. Wound layers are sutured. Drainage is optional.

POSTOPERATIVE MANAGEMENT

Sterile wound dressing; compressive bandage. No limitation of the active and passive range of motion. Optional partial weight bearing during the first 2 weeks, then transition to full weight bearing. Follow-up directly after surgery, at 12 and 52 weeks, then every 1-2 years.

RESULTS

Overall 60 patients with tricompartmental knee OA and preserved PCL were treated. Mean age was 66 (range 45-76) years. Minimum follow-up was 12 months. There was 1 septic revision after a low-grade infection, 1 reoperation to replace the patellar due to patellar osteoarthritis and 3 manipulations under anesthesia (MUAs) to increase range of motion. Radiographic analyses demonstrated an ideal implant fit with less than 2 mm subsidence or overhang. The WOMAC score improved from 154.8 points preoperatively to 83.5 points at 1 year and 59.3 points at 2 years postoperatively. The EuroQol-5D Score also improved from 11.1 points preoperatively to 7.7 points at 1 year postoperatively.

Radiological Society of North America (RSNA) 3D printing Special Interest Group (SIG): guidelines for medical 3D printing and appropriateness for clinical scenarios

Medical three-dimensional (3D) printing has expanded dramatically over the past three decades with growth in both facility adoption and the variety of medical applications. Consideration for each step required to create accurate 3D printed models from medical imaging data impacts patient care and management. In this paper, a writing group representing the Radiological Society of North America Special Interest Group on 3D Printing (SIG) provides recommendations that have been vetted and voted on by the SIG active membership. This body of work includes appropriate clinical use of anatomic models 3D printed for diagnostic use in the care of patients with specific medical conditions. The recommendations provide guidance for approaches and tools in medical 3D printing, from image acquisition, segmentation of the desired anatomy intended for 3D printing, creation of a 3D-printable model, and post-processing of 3D printed anatomic models for patient care.

Soft-tissue damage during total knee arthroplasty: Focus on tourniquet-induced metabolic and ionic muscle impairment

PURPOSE

Advantages of tourniquet use in TKA include benefits for surgeons and patients, varying from a bloodless operation site to a reduced intervention time. The time under ischemia and the reperfusion period are crucial phases for affected soft-tissue, most commonly the extensor mechanism.

CASE REPORTS

documented its impact on soft-tissue, ranging from necrotic muscle damage to systemic inflammation. Recently, research regarding tourniquet application patterns discuss clinical outcome parameters in the context of soft-tissue damage, excluding the underlying pathophysiological mechanisms.

METHODS

This review summarizes the molecular aspects of soft-tissue damage occurring during tourniquet application in TKA with special focus on ischemia/reperfusion injury. Recent meta-analyses and original trials were reviewed for data on muscle damage and are presented.

CONCLUSION

Although underlying pathomechanisms are well known and presented, clinical orthopedic research has so far not addressed this issue. In context of physical training, positive effects regarding postoperative recovery might be possible if more attention is paid to prepare involved muscle preoperatively to TKA (prehabilitation).