Is the Anterior Tibial Tuberosity a Reliable Rotational Landmark for the Tibial Component in Total Knee Arthroplasy?

To analyze the morphology of the tibial plateau, we studied 100 computed tomographic scans of arthritic knees and measured the mediolateral (ML) and anteroposterior (AP) dimensions as well as their aspect ratio using 3 reference axes of rotation: transepicondylar axis (TEA), posterior tibial margin (PTM), and anterior tibial tuberosity (ATT) axis. Relative to the TEA, the PTM was internally rotated by 1.6° ± 5.1°, and the ATT externally rotated by 14.8° ± 7.2°. The AP and ML dimensions and aspect ratio differ significantly when the reference axis was ATT compared with PTM or TEA and variations were greater while using ATT axis. Our data demonstrate (1) that design of the tibial component restricts the choice of rotational alignment and (2) that ATT is not a reliable landmark for rotation of the tibial component.     

DIAGNOSIS OF CHRONIC PANCREATITIS: Is a Gold Standard Necessary?

The question that serves as this article's title is rhetorical. Clinicians have diagnosed and managed chronic pancreatitis without a gold standard for decades and must continue to do so in the foreseeable future. Although clinicians have a much wider array of diagnostic tools available for the diagnosis of chronic pancreatitis, a single readily applied gold standard remains elusive. Diagnostic studies are rarely compared with a true gold standard--histopathology. Furthermore, even if a safe biopsy technique were available, it might fall short of a gold standard, given the patchy nature of early-stage chronic pancreatitis. Indeed, different stages of chronic pancreatitis require not only recognition of the different clinical presentations but also different levels of intensity of diagnostic testing to establish the diagnosis confidently. The diagnosis in most patients with chronic pancreatitis can be made confidently with a good clinical history and a limited number of currently available structural and functional tests. No single diagnostic study, functional or structural, suffices for all patients. It is also axiomatic that patients with intractable abdominal pain in whom early-stage chronic pancreatitis is suspected represent a challenge for clinicians partly because of this lack of a single, dependable gold standard. Perhaps we have reached the point at which further refinements of current tests of structure or function are not beneficial because increased sensitivity is countered by loss of specificity. We suggest that a new approach to developing a gold standard for the diagnosis of chronic pancreatitis is necessary. With advances in the understanding of the mediators of the inflammatory process, it may be possible to devise a test to assess the earliest events in this disease.     

Is There a Threshold for Stiffness Complaints Following TKA on the WOMAC Stiffness Subscale?

Background

Stiffness complaints after total knee arthroplasty (TKA) are frequent, yet poorly understood and can be challenging for surgeons to address. The WOMAC stiffness subscale is a widely used measure of stiffness and can serve as a simple screening tool for complaints.

Questions/Purposes

We aimed to identify a threshold for stiffness complaints on the WOMAC stiffness subscale and investigate its overlap with range of motion (ROM) in TKA patients.

Methods

TKA patients were enrolled preoperatively and followed for 6 months. At follow-up, patients reported their ROM, completed the WOMAC stiffness subscale (range 1–8 with 8 continuous stiffness) and indicated whether they experienced more stiffness than expected. To identify a threshold for complaints, we compared patients’ WOMAC stiffness scores to when they experienced more stiffness than expected, visually, and statistically. We also mapped ROM limitations at 6 months to WOMAC stiffness scores. Finally, we determined if baseline characteristics were associated with stiffness complaints.

Results

Two hundred and forty-six TKA patients were enrolled preoperatively with 82% follow-up rate at 6 months. Our results showed that patients with a WOMAC stiffness score?=?3+ were significantly more likely to experience more stiffness than expected. Patients reporting full ROM (54%) reported a wide range of WOMAC stiffness subscale scores (1–6). Baseline WOMAC pain and function scores were the only factors associated with stiffness complaints.

Conclusions

ROM is a poor surrogate of patient-reported stiffness, and the patients’ perception of “stiffness” is clearly more complex than just ROM. We identified a WOMAC threshold that could potentially easily serve this purpose.

     

Are We Misdiagnosing Diabetic Foot Osteomyelitis? Is the Gold Standard Gold?

To compare the incidence of osteomyelitis based on different operational definitions using the gold standard of bone biopsy, we prospectively enrolled 35 consecutive patients who met the criteria of ≥21 years of age and a moderate or severe infection based on the Infectious Diseases Society of America classification. Bone samples were obtained from all patients by percutaneous bone biopsy or intraoperative culture if the patient required surgery. Bone samples were analyzed for conventional culture, histology, and 16S ribosomal RNA genetic sequencing. We evaluated 5 definitions for osteomyelitis: 1) traditional culture, 2) histology, 3) genetic sequencing, 4) traditional culture and histology, and 5) genetic sequencing and histology. There was variability in the incidence of osteomyelitis based on the diagnostic criteria. Traditional cultures identified more cases of osteomyelitis than histology (68.6% versus 45.7%, p = .06, odds ratio [OR] 2.59, 95% confidence interval [CI] 0.98 to 6.87), but the difference was not significant. In every case that histology reported osteomyelitis, bone culture was positive using traditional culture or genetic sequencing. The 16S ribosomal RNA testing identified significantly more cases of osteomyelitis compared with histology (82.9% versus 45.7%, p = .002, OR 5.74, 95% CI 1.91 to 17.28) and compared with traditional cultures but not significantly (82.9% versus 68.6%, p = .17, OR 2.22, 95% CI 0.71 to 6.87). When both histology and traditional culture (68.6%) or histology and genetic sequencing cultures (82.9%) were used to define osteomyelitis, the incidence of osteomyelitis did not change. There is variability in the incidence of osteomyelitis based on how the gold standard of bone biopsy is defined in diabetic foot infections.     

Is There Still a Place for Face-to-Face Meetings?

There is definitely an essential place for face-to-face meetings. We renew bonds; affirm and expand diversity; learn and share as both students and mentors; advance the field to the benefit of our patients; and gain wisdom from experienced and devoted leaders.     

Is Femoral Component Rotation in a TKA Reliably Guided by the Functional Flexion Axis?

Background

The position of the femoral component in a TKA in the axial plane influences patellar tracking and flexion gap symmetry. Errors in femoral component rotation have been implicated in the need for early revision surgery. Methods of guiding femoral component rotation at the time of implantation typically are derived from the mean position of the flexion-extension axis across experimental subjects. The functional flexion axis (FFA) of the knee is kinematically derived and therefore a patient-specific reference axis that can be determined intraoperatively by a computer navigation system as an alternative method of guiding femoral component rotation. However, it is unclear whether the FFA is reliable and how it compares with traditional methods.

Question/purposes

We asked if the FFA could be measured reproducibly at different stages of the operative procedure; (2) where it lies in relation to a CT-derived gold standard; and (3) how it compares with more traditional methods of judging femoral component rotation.

Methods

Thirty-seven patients undergoing elective TKAs were recruited to the study. Preoperative CT scans were obtained and the transepicondylar axis (TEA) was identified. The TKA then was performed using computer navigation. The FFA was derived before incision and again after the surgical approach and osseous registration. The navigation system was used to register the surgical TEA. The FFA and surgical TEA then were compared with the CT-derived TEA.

Results

The mean preincision FFA was similar to the intraoperative FFA and therefore deemed reproducible. We observed no differences in variability between surgical TEA and preincision FFA. The FFA was different from the CT-TEA and judged similar in accuracy to the surgical TEA.

Conclusion

The reliability and accuracy of the FFA were similar to those of other intraoperative methods. Further evaluation is required to ascertain whether the FFA improves on currently available methods for determining the ideal rotation of the femoral component during TKA.     

Are Acetabular Component Alignment Guides for Total Hip Arthroplasty Accurate?

The acetabular component orientation of total hip arthroplasty is of critical importance to the clinical results. Although navigation systems have recently been introduced, acetabular component alignment guides are still used in most of ordinary hospitals. However, the accuracy of alignment guides themselves has not been evaluated. Fifteen types of alignment guide were examined. In all the alignment guides, the angles actually indicated and those stated by manufacturers were different. Our results showed that usage of modern alignment guides inherently misleads anteversion into decrease by a mean of 6° (maximum, 12°) and inclination into increase by a mean of 2° (maximum: 4°). Such setting of alignment guides could be one of the factors of error in acetabular component orientation.     

Does Imageless Computer-assisted TKA Lead to Improved Rotational Alignment or Fewer Outliers? A Systematic Review

Background

Computer-assisted surgery (CAS) has been developed to enhance prosthetic alignment during primary TKAs. Imageless CAS improves coronal and sagittal alignment compared with conventional TKA. However, the effect of imageless CAS on rotational alignment remains unclear.

Questions/purposes

We conducted a systematic and qualitative review of the current literature regarding the effectiveness of imageless CAS during TKA on (1) rotational alignment of the femoral and tibial components and tibiofemoral mismatch in terms of deviation from neutral rotation, and (2) the number of femoral and tibial rotational outliers.

Methods

Data sources included PubMed, MEDLINE, and EMBASE. Study selection, data extraction, and methodologic quality assessment were conducted independently by two reviewers. Standardized mean difference with 95% CI was calculated for continuous variables (rotational alignment of the femoral or tibial component and tibiofemoral mismatch). To compare the number of outliers for femoral and tibial component rotation, the odds ratio and 95% CI were calculated. The literature search produced 657 potentially relevant studies, 17 of which met the inclusion criteria. One study was considered as having high methodologic quality, 15 studies had medium, and one study had low quality.

Results

Conflicting evidence was found for all outcome measures except for tibiofemoral mismatch. Moderate evidence was found that imageless CAS had no influence on postoperative tibiofemoral mismatch. The measurement protocol for measuring tibial rotation varied among the studies and in only one of the studies was the sample size calculation based on one of the outcome measures used in our systematic review.

Conclusions

More studies of high methodologic quality and with a sample size calculation based on the outcome measures will be helpful to assess whether an imageless CAS TKA improves femoral and tibial rotational alignment and tibiofemoral mismatch or decreases the number of femoral and tibial rotational outliers. To statistically analyze the results of different studies, the same measurement protocol should be used among the studies.

Electronic supplementary material

The online version of this article (doi:10.1007/s11999-014-3688-5) contains supplementary material, which is available to authorized users.     

MRI After Patellofemoral Replacement: the Component–Bone Interface and Rotational Alignment

Background

In an earlier paper, it was shown that tailored magnetic resonance imaging (MRI) allows for reproducible analysis of the preserved knee joint structures after patellofemoral replacement (PFR).

Purposes

This pilot study investigates to what degree MRI could produce reliable assessment of the implant–bone interface of femoral and patellar components and rotational alignment following PFR.

Methods

MRI tailored for reduction of metallic artefacts was performed in seven patients who had undergone PFR. Two independent investigators evaluated the implant–bone interface at femoral and patellar components and the rotational alignment of the femoral component. They also assessed their degree of confidence in evaluation using a five-point scale. The inter-observer reliability was determined.

Results

Implant-induced MRI artefact was barely observed and there was no interference with component–bone interface evaluation. There was excellent inter-observer reliability, inter-observer agreement, and confidence for the implant–bone interface at femoral and patellar components and for rotational alignment. The applied score for the interface was found to be reliable.

Conclusion

Tailored MRI allows reproducible analysis of the implant–bone interface and of rotational alignment of the femoral component in patients who have had PFR. It might prove helpful in the assessment of painful PFR.

Electronic supplementary material

The online version of this article (doi:10.1007/s11420-013-9336-x) contains supplementary material, which is available to authorized users.     

Is the Medial Wall of the Intercondylar Notch Useful for Tibial Rotational Reference in Unicompartmental Knee Arthroplasty?

Background  

It is difficult to implant components in the correct rotational position in the narrow operating field in a unicompartmental knee arthroplasty. Although no rotational reference has been confirmed for unicompartmental knee arthroplasty, the AP axis of the tibia may serve as a reference for unicompartmental knee arthroplasty and TKA. However, it is difficult to identify the AP axis during unicompartmental knee arthroplasty, especially with the tibia first-cut technique.     

Is There a Role for Bisphosphonates in Chronic Kidney Disease?

Patients with stage 5 chronic kidney disease (CKD) including those on dialysis can and do develop osteoporosis. They also develop a wide range of other metabolic bone diseases that may look like osteoporosis when it is defined by either the World Health Organization bone mineral density (BMD) criteria or by the development of fragility fractures. Those dialysis patients with osteoporosis that is due to gonadal hormone deficiency such as postmenopausal osteoporosis, glucocorticoid-induced osteoporosis, or male osteoporosis may benefit from the administration of bisphosphonates (BPs). The challenges lie in the diagnosis of osteoporosis in this population where adynamic, osteomalacic, hyperparathyroid, or aluminum bone disease are also prevalent, with concommitant low BMD and low trauma fractures, but where BPs may be contraindicated. The only secure means to diagnose osteoporosis in this patient population is by quantitative bone histomorphometry demonstrating low trabecular bone volume and disrupted microarchitecture. Once the diagnosis of osteoporosis is established, BPs should be considered for a well-defined brief period of time (e.g., 2-3 years), even though there is no evidence for a fracture reduction benefit in this population. If a BP is chosen there may be a need for dose adjustment or slower infusion rates (for the intravenous formulations), as a greater bone retention may occur for these renally cleared agents. While it is unknown what consequences could develop from increased bone retention in patients with little renal function, data are needed if more bone retention of BP might lead to a greater risk of the development of adynamic bone disease and lower bone strength. More data are needed to define the risks and benefits of BPs in patients with stage 5 CKD.