Revision of partial knee to total knee arthroplasty with use of patient-specific instruments results in acceptable femoral rotation

Patient-specific guides in orthopedic surgery

The interest of patient-specific guides (PSGs) lies in reliable intraoperative achievement of preoperative planning goals. They are a form of instrumentation optimizing intraoperative precision and thus improving the safety and reproducibility of surgical procedures. Clinical superiority, however, has not been demonstrated. The various steps from design to implementation leave room for error, which needs to be known and controlled by the surgeon who is responsible for final outcome. Instituting large-scale patient-specific surgery requires management systems for guides and innovative implants which cannot be a simple extension of current practices. We shall approach the present state of knowledge regarding PSGs via 5 questions: (1) What is a PSG? Single-use instrumentation produced after preoperative planning, aiming exclusively to optimize procedural exactness. (2) How to use and assess PSGs in orthopedic surgery? Strict rules of use must be adhered to. Any deviation from the predefined objective is, necessarily, an error that must be identified as such. (3) Do PSGs provide greater surgical exactness? The contribution of PSGs varies greatly between procedures. Exactness is enhanced in the spine, in osteotomies around the knee and in bone-tumor surgery. In the shoulder, their contribution is seen only in complex cases. Data are sparse for hip replacement, and controversial for knee replacement. (4) What are the expected benefits of PSGs? As well as improving exactness, PSGs allow a lower radiation dose and shorter operating time. They also enable junior surgeons to train in techniques otherwise reserved to hyperspecialists. (5) How to include PSGs in everyday practice? As well as their potential clinical interest, PSGs involve deep changes in organization, equipment provision and economic model. LEVEL OF EVIDENCE: V; expert opinion.

Comparable incidence of periprosthetic tibial fractures in cementless and cemented unicompartmental knee arthroplasty: a systematic review and meta-analysis

PURPOSE

(I) To determine the incidence of periprosthetic tibial fractures in cemented and cementless unicompartmental knee arthroplasty (UKA) and (II) to summarize the existing evidence on characteristics and risk factors of periprosthetic fractures in UKA.

METHODS

Pubmed, Cochrane and Embase databases were comprehensively searched. Any clinical, laboratory or case report study describing information on proportion, characteristics or risk factors of periprosthetic tibial fractures in UKA was included. Proportion meta-analysis was performed to estimate the incidence of fractures only using data from clinical studies. Information on characteristics and risk factors was evaluated and summarized.

RESULTS

A total of 81 studies were considered to be eligible for inclusion. Based on 41 clinical studies, incidences of fractures were 1.24% (95%CI 0.64-2.41) for cementless and 1.58% (95%CI 1.06-2.36) for cemented UKAs (9451 UKAs). The majority of fractures in the current literature occurred during surgery or presented within 3 months postoperatively (91 of 127; 72%) and were non-traumatic (95 of 113; 84%). Six different fracture types were observed in 21 available radiographs. Laboratory studies revealed that an excessive interference fit (press fit), excessive tibial bone resection, a sagittal cut too deep posteriorly and low bone mineral density (BMD) reduce the force required for a periprosthetic tibial fracture to occur. Clinical studies showed that periprosthetic tibial fractures were associated with increased body mass index and postoperative alignment angles, advanced age, decreased BMD, female gender, and a very overhanging medial tibial condyle.

CONCLUSION

Comparable low incidences of periprosthetic tibial fractures in cementless and cemented UKA can be achieved. However, surgeons should be aware that an excessive interference fit in cementless UKAs in combination with an impaction technique may introduce an additional risk, and could therefore be less forgiving to surgical errors and patients who are at higher risk of periprosthetic tibial fractures.

LEVEL OF EVIDENCE

V.

Revision of total knee arthroplasty with the use of patient-specific instruments: an alternative surgical technique

INTRODUCTION

Accuracy in the placement of components in revision total knee arthroplasty (R-TKA) surgery is sometimes challenging. The applicability of patient‑specific instruments (PSI) in knee surgery has progressively expanded to types of surgery other than primary arthroplasty. Could this assistive technology be used to facilitate accurate R-TKA surgery? The aim of the current manuscript is to describe this new application of PSI for revision of TKA-to-TKA and to provide a step-by-step technical guideline for use.

AREAS COVERED

We will describe the application and a detailed description of PSI technology to TKA revision surgery, step-by-step, from CT images acquisition for preoperative planning and PSI blocks production to the surgery.

EXPERT COMMENTARY

The system can facilitate the accomplishment of the bony cuts for optimal implant placement and that can be useful in minimally altering the femoral and the tibial joint line. It is obvious that technology alone will not replace surgical skill and that accuracy of the system will also depend on the quality of the CT images and the ability of the software to prevent metal artifacts. Despite that, our initial results are promising and prove that the concept of applying PSI technology to the R-TKA surgery is feasible.

No difference in mid-term survival and clinical outcome between patient-specific and conventional instrumented total knee arthroplasty: a randomized controlled trial

PURPOSE

The purpose of this multicentre prospective randomized controlled trial was to compare the survival rate and clinical outcome in total knee arthroplasty (TKA) after MRI-based patient-specific instruments (PSI) and conventional instruments 5 years after initial surgery.

METHODS

At a mean follow-up of 5.1 years (0.4), 163 patients (90.6%) with a mean age of 71.8 years (8.7) were analysed. A survival analysis with revision of the TKA as endpoint was performed. The Knee Society Score (KSS), evaluations on plain radiographs and patient-reported outcome measures (PROMs) were obtained preoperatively and at each FU.

RESULTS

At final follow-up, one TKA in the PSI- (1.2%) and 3 TKAs in the conventional group (3.8%) had undergone revision surgery (n.s.). No radiological abnormalities were noted at any time point. Postoperatively, the KSS and PROMs significantly improved within each group compared with the preoperative values. There were no clinically relevant differences for the KSS [PSI: 77.4, 9.8 (95% CI 75.0-79.7) vs. conventional: 77.3 10.5 (95% CI 74.9-79.8)] and the PROMs between both groups (n.s.) at 5 years follow-up.

CONCLUSION

There is still a lack of reliable data on the survival of TKA and clinical evidence, when using PSI for TKA. Longer follow-up studies are, therefore, needed.

LEVEL OF EVIDENCE

I.

Patient-specific instrumentation in Oxford unicompartmental knee arthroplasty is reliable and accurate except for the tibial rotation

PURPOSE

Patient-specific instrumentation (PSI) is a technique to plan and position the prosthesis components in unicompartmental knee arthroplasty (UKA) surgery. This study assesses whether the definitive component position in the frontal, sagittal and axial plane is according to the preoperative plan, based on the hypothesis that PSI is accurate.

METHODS

Twenty-six patients who had PSI Oxford UKA surgery were included prospectively. The component position in vivo was determined with a postoperative CT-scan and compared with the planned component position using MRI-based digital 3D imaging. Adjustments to the preoperative plan and implanted component sizes during surgery were recorded.

RESULTS

Intraoperatively, no femoral adjustments were performed; 12 tibial re-resections were necessary. The median absolute deviation from the plan in degrees (range) in the frontal, sagittal and axial plane was 1.8° (- 1.5°-6.5°), 2.0° (- 6.5°-8.0°) and 1.0° (- 1.5°-5.0°) for the femoral component, and 2.5° (- 1.0°-6.0°), 3.0° (- 1.0°-5.0°) and 5.0° (- 6.5°-12.5°) for the tibial component. The femoral component is positioned 0.5 (- 1°-2.5°) mm more lateral and 0.8 (- 1.0°-2.5°) mm more anterior. The tibial component is positioned 2.0 (- 5.0-0.0) mm more lateral and 1.3 (- 3.0-6.0) mm more distal. The femoral and tibial default plans were changed four times (15.4%) and nine times (34.6%), respectively, before approval by the surgeon.

CONCLUSION

PSI in Oxford UKA surgery is reliable and accurately translates the preoperative plan into the in vivo situation, except for the tibial rotational position. The preoperative planning is a crucial step in avoiding re-resections that can cause angular deviations in prosthesis position, especially in tibial component rotational position. It is advised to avoid re-resections and to consider this while planning the PSI procedure.

LEVEL OF EVIDENCE

Prospective comparative study Level II.

Clinical Outcome of Total Knee Arthroplasty Performed Using Patient-Specific Cutting Guides

Background

Patient-specific instruments have recently gained attention for ensuring the accuracy of osteotomy and correct alignment in total knee arthroplasty (TKA). We aimed to report our experience with TKA performed by using CT-based 3D model of cutting guides in our clinic.

Material/Methods

A total of 36 patients (mean age, 67.58±8.46 years; 24 females, 12 males) who underwent TKA with 3D patient-specific cutting guides in our clinic were included in the study. Differences between preoperatively planned bone resections and actual bone resections were calculated. Femoral and tibial component angles were measured on radiographs of the knee. The change in knee pain was evaluated by patients on a 10-point visual analog scale (VAS). Patients were followed up for 6 months postoperatively.

Results

The actual bone resection was 0.5–1.5 mm higher than the planned resection for all sides, being statistically significant for posterior lateral and distal medial sides (1.1±1.3 mm and 1.5±0.9 mm, respectively; p<0.05). On postoperative radiographs, coronal tibial component angle was 88.8°±0.9° and coronal femoral component angle was 95.2°±1.6°, showing good postoperative alignment. The VAS pain score of patients significantly decreased from preoperative 3.9±0.8 to 1.1±0.9 at 6 months after the operation. One patient developed superficial tissue infection on postoperative follow-up, which was effectively treated. No other pathology was detected in the postoperative period.

Conclusions

Patient-specific cutting guides can provide intraoperative guidance for better placement of the implant in TKA and increase the accuracy of osteotomy and postoperative alignment.