Load-induced deformation of the tibia and its effect on implant loosening detection

CT imaging under external valgus and varus loading conditions and consecutive image analysis can be used to detect tibial implant loosening after total knee arthroplasty. However, the applied load causes the tibia to deform, which could result in an overestimation of implant displacement. This research evaluates the extent of tibia deformation and its effect on measuring implant displacement. Ten cadaver specimen with TKA were CT-scanned under valgus/varus loading (20 Nm), first implanted without bone cement fixation (mimicking a loose implant) and subsequently with bone cement fixation (mimicking a fixed implant). By means of image analysis, three relative displacements were assessed: (1) between the proximal and distal tibia (measure of deformation), (2) between the implant and the whole tibia (including potential deformation effect) and (3) between the implant and the proximal tibia (reduced deformation effect). Relative displacements were quantified in terms of translations along, and rotations about the axes of a local coordinate system. As a measure of deformation, the proximal tibia moved relative to the distal tibia by, on average 1.27 mm (± 0.50 mm) and 0.64° (± 0.25°). Deformation caused an overestimation of implant displacement in the cemented implant. The implant displaced with respect to the whole tibia by 0.45 mm (± 0.22 mm) and 0.79° (± 0.38°). Relative to the proximal tibia, the implant moved by 0.23 mm (± 0.10 mm) and 0.62° (± 0.34°). The differentiation between loose and fixed implants improved when tibia deformation was compensated for by using the proximal tibia rather than the whole tibia.

Does Consulting an Occupational Medicine Specialist Decrease Time to Return to Work Among Total Knee Arthroplasty Patients? A 12-Month Prospective Multicenter Cohort Study

PURPOSE

The aim of this study is to investigate whether total knee arthroplasty (TKA) patients who consulted an occupational medicine specialist (OMS) within 3 months after surgery, return to work (RTW) earlier than patients who did not consult an OMS.

METHODS

A multi-center prospective cohort study was performed among working TKA patients, aged 18 to 65 years and intending to RTW. Time to RTW was analyzed using Kaplan Meier and Mann Whitney U (MWU), and multiple linear regression analysis was used to adjust for effect modification and confounding.

RESULTS

One hundred and eighty-two (182) patients were included with a median age of 59 years [IQR 54-62], including 95 women (52%). Patients who consulted an OMS were less often self-employed but did not differ on other patient and work-related characteristics. TKA patients who consulted an OMS returned to work later than those who did not (median 78 versus 62 days, MWU p < 0.01). The effect of consulting an OMS on time to RTW was modified by patients' expectations in linear regression analysis (p = 0.05). A median decrease in time of 24 days was found in TKA patients with preoperative high expectations not consulting an OMS (p = 0.03), not in patients with low expectations.

CONCLUSIONS

Consulting an OMS within 3 months after surgery did not result in a decrease in time to RTW in TKA patients. TKA patients with high expectations did RTW earlier without consulting an OMS. Intervention studies on how OMSs can positively influence a timely RTW, incorporating patients' preoperative expectations, are needed.

Beneficial and limiting factors in return to work after primary total knee replacement: Patients' perspective

BACKGROUND:

Return to work (RTW) is an important outcome in Total Knee Arthroplasty (TKA). At present, 70–80%of TKA patients return to work within three to six months.

OBJECTIVE:

What are patients’ perspectives regarding beneficial and limiting factors in RTW after TKA?

METHODS:

Focus groups were formed in accordance with the Consolidated Criteria for Reporting Qualitative Research (COREQ) checklist. Three major topics were explored: 1. What was beneficial for RTW after TKA; 2. What was limiting for RTW after TKA; and 3. What additional care would benefit RTW after TKA?

RESULTS:

Data saturation was reached after four focus groups, comprising 17 participants—nine men and eight women (median age 58, range 52–65). The focus group study identified four main themes that contributed to a successful RTW namely rehabilitation (medical) like post-operative physical therapy, patient characteristics (personal), like motivation to RTW, occupational characteristics (work-related) like build-up in work tasks and medical support (medical) like availability of a walker or crutches.

CONCLUSION:

According to participants, factors within the following four themes can contribute to a successful return to work: occupational, patient, rehabilitation and medical care. Incorporating these factors into the integrated care pathway for the “young” TKA patients may increase the chances of a successful RTW.

Cryotherapy after Total Knee Arthroplasty provides faster recovery and better ranges of motion in short term follow up. Results of a prospective comparative study

Cryotherapy is applied in Total Knee Arthroplasty (TKA) to improve functional outcome. The aim of this study is to investigate whether an advanced cryotherapy device does not increase the risk of complications and improves knee function or decreases swelling. A prospective cohort of TKA patients was formed by a cryotherapy group and a control group. The primary outcome was complication ratio. Our secondary outcomes were functional results and swelling. No significant differences were found in complication ratio between 31 patients in the cryotherapy group and 31 patients in the control group. The cryotherapy group showed a significant better knee flexion and less swelling in the early rehabilitation phase. No differences were found at the other follow-up moments or in the other outcomes. This advanced cryotherapy device is safe in respect of postoperative complications, improves knee function and decreases swelling in the early rehabilitation phase. However, it is questionable if an advanced cryotherapy device with its additional costs is necessary to provide the desired effects of cryotherapy.

Predicted osteotomy planes are accurate when using patient-specific instrumentation for total knee arthroplasty in cadavers: a descriptive analysis

PURPOSE

Malalignment of implants is a major source of failure during total knee arthroplasty. To achieve more accurate 3D planning and execution of the osteotomy cuts during surgery, the Signature (Biomet, Warsaw) patient-specific instrumentation (PSI) was used to produce pin guides for the positioning of the osteotomy blocks by means of computer-aided manufacture based on CT scan images. The research question of this study is: what is the transfer accuracy of osteotomy planes predicted by the Signature PSI system for preoperative 3D planning and intraoperative block-guided pin placement to perform total knee arthroplasty procedures?

METHODS

The transfer accuracy achieved by using the Signature PSI system was evaluated by comparing the osteotomy planes predicted preoperatively with the osteotomy planes seen intraoperatively in human cadaveric legs. Outcomes were measured in terms of translational and rotational errors (varus, valgus, flexion, extension and axial rotation) for both tibia and femur osteotomies.

RESULTS

Average translational errors between the osteotomy planes predicted using the Signature system and the actual osteotomy planes achieved was 0.8 mm (± 0.5 mm) for the tibia and 0.7 mm (± 4.0 mm) for the femur. Average rotational errors in relation to predicted and achieved osteotomy planes were 0.1° (± 1.2°) of varus and 0.4° (± 1.7°) of anterior slope (extension) for the tibia, and 2.8° (± 2.0°) of varus and 0.9° (± 2.7°) of flexion and 1.4° (± 2.2°) of external rotation for the femur.

CONCLUSION

The similarity between osteotomy planes predicted using the Signature system and osteotomy planes actually achieved was excellent for the tibia although some discrepancies were seen for the femur. The use of 3D system techniques in TKA surgery can provide accurate intraoperative guidance, especially for patients with deformed bone, tailored to individual patients and ensure better placement of the implant.

Electrocardiographic abnormalities in patients admitted for hip fracture

BACKGROUND

Several risk factors for falls and hip fractures have been recognised, but controversy still exists regarding the importance of rhythm and conduction abnormalities as potentially modifiable risk factors for recurrent falls. The aim of this study was to determine the prevalence of clinically relevant ECG abnormalities in patients with a hip fracture versus controls.

METHODS

The study was designed as a case-control study within consecutive hip surgery patients in an academic hospital.

CASES

patients with traumatic hip fractures.

CONTROLS

patients undergoing planned hip surgery (non-traumatic). CASES and controls were 1:1 matched for age and gender.

INCLUSION CRITERIA

age &#8805; 50 years.

EXCLUSION CRITERIA

high-energy trauma, pathological and÷or previous hip fracture. ECGs were scored using predefined categories. Multivariate logistic regression was performed to calculate odds ratios (OR) and to correct for confounders.

RESULTS

We included 888 patients (444 cases). Mean age was 70.9 years (SD 9.3), 70% were female. After correction for potential confounders we found the following associations between clinically relevant ECG abnormalities and hip fractures: atrial fibrillation OR 2.7 (95% CI 1.2-6.1), abnormal QTc prolongation OR 3.9 (2.2-6.8), sinus tachycardia OR 5.0 (2.1-11.8) and sinus bradycardia OR 0.3 (0.1-0.5). Univariately, several markers for decreased cardiac function were also associated with hip fractures.

CONCLUSIONS

Hip fracture patients are at higher risk for ECG abnormalities than matched patients undergoing hip surgery for other indications. To potentially reduce the risk of future (injurious) falls, increased awareness of these ECG abnormalities is warranted to assess the need for further cardiovascular fall risk assessment.

Variation in joint stressing magnitudes during knee arthroscopy

PURPOSE

When performing knee arthroscopy, joint stressing is essential to increase the operative joint space. Adequate training of joint stressing is important, since high stressing forces can damage knee ligaments, and low stressing might not give sufficient operative space. As forces are difficult to transfer since they cannot be seen, simulators might be suited to train joint stressing as they can visualise the amount of applied stress. This requires the joint stressing thresholds to be validated. The purpose of this study was to measure the variation in the maximum joint stressing forces applied by various surgeons in vivo in a human population and based on that derive thresholds for safe stressing.

METHODS

From studies on ligament failure properties, we inferred a theoretical maximum stressing force of 78 N. Twenty-one patients were included, and knee arthroscopies were performed by five experienced surgeons. Forces solely performed in the varus and in valgus direction were measured. A load sensor was mounted on a belt, which was rotated along the hip to measure both varus and valgus stressing. The measurements started as soon as the interior of the knee joint was visualised using joint stressing.

RESULTS

The average maximum stressing force was 60 N (SD = 28 N). The mean first frame force was 47 N (SD = 34 N). No significant differences were found between varus and valgus stressing.

CONCLUSION

Since variation in stressing forces is high, offering training cases on simulators where the complete range of stressing forces can be experienced is recommended. Abiding to safety levels is essential to increase patient safety.

Evaluation of a CT-based technique to measure the transfer accuracy of a virtually planned osteotomy

Accurate transfer of a preoperatively planned osteotomy plane to the bone is of significance for corrective surgery, tumor resection, implant positioning and evaluation of new osteotomy techniques. Methods for comparing a preoperatively planned osteotomy plane with a surgical cut exist but the accuracy of these techniques are either limited or unknown. This paper proposes and evaluates a CT-based technique that enables comparing virtual with actual osteotomy planes. The methodological accuracy and reproducibility of the technique is evaluated using CT-derived volume data of a cadaver limb, which serves to plan TKA osteotomies in 3-D space and to simulate perfect osteotomies not hampered by surgical errors. The methodological variability of the technique is further investigated with repeated CT scans after actual osteotomy surgery of the same cadaver specimen. Plane displacement (derr) and angulation errors in the sagittal and coronal plane (βerr, γerr) are measured with high accuracy and reproducibility (derr=-0.11±0.06mm; βerr=0.08±0.04°, γerr=-0.03±0.03°). The proposed method for evaluating an osteotomy plane position and orientation has a high intrinsic accuracy and reproducibility. The method can be of great value for measuring the transfer accuracy of new techniques for positioning and orienting a surgical cut in 3-D space.

[One-stage bilateral total hip arthroplasty: a systematic review and meta-analysis]

OBJECTIVE

To investigate whether bilateral total hip arthroplasty (THA) performed in one session is a safe procedure.

DESIGN

Systematic review.

METHOD

In a literature search, 1460 studies were found of which 5 prospective in nature and which met our inclusion criteria. The patient data from these studies were pooled for meta-analysis. Data from 579 patients could be pooled for the two-session bilateral THA group and data from 334 patients for the one-session THA group.

RESULTS

After this pooling of data, no difference in major complications was found (odds ratio: 0.72; 95%-CI: 0.45-1.15). Minor complications occurred more often in the one-session group (odds ratio: 0.50; 95%-CI: 0.32-0.78). Intra-operative blood loss was less in the one-session group (121.7 ml; 95%-CI: 51.6-191.9), whilst the number of transfusions was greater in this group than in the two-session group (-0.5 units; 95%-CI: -0.74--0.20). Duration of the surgical procedure was not influenced by the choice for one or two sessions (difference: 6.0 minutes; 95%-CI: -2.4-14.4). Length of hospital stay was significantly shorter in the one-session group (3.2 days; 95%-CI: 3.0-3.7).

CONCLUSION

We conclude that one-session bilateral THA appears to be a safe procedure in selected patients.