Reading the Small Print – Labelling Recommendations for Orthopaedic Implants

INTRODUCTION

There exist, currently, no clear guidelines regarding standards for surgical implant labelling. Dimensions of the laminar flow canopies in orthopaedic use fixes the distance at which implant labels can be read. Mistakes when reading the label on an implant box can pose health risks for patients, and financial consequences for medical institutions.

SUBJECTS AND METHODS

Using scientifically validated tools such as the Snellen Chart Formula, a theoretical minimum standard for text on implant labels was reached. This theoretical standard was then tested under real operating conditions. After discovering a minimum practical standard for implant labels, the authors then audited current labels in use on a wide range of orthopaedic implant packages. Furthermore, other non-text-related labelling problems were also noted.

RESULTS

There is a definite minimum standard which should be observed when implant labels are manufactured. Implants in current use bear labels on the packaging that are of an insufficient standard to ensure patient safety in theatre.

CONCLUSIONS

The authors have established text parameters that will increase the legibility of implant labels. In the interests of improving risk management in theatre, therefore, the authors propose a standard for orthopaedic implant labelling, and believe this will provide a useful foundation for further discussion between the orthopaedic community and implant manufacturers.     

Mid-Term Functionality and Survival of 116 HemiCAP® Implants for Hallux Rigidus

Hallux rigidus can be treated with a proximal hemiarthroplasty (HemiCAP®) to preserve the motion in the first metatarsophalangeal joint and reduce pain. This study examines the functionality, and survival rates of HemiCAP® implants, with or without a dorsal flange. One hundred and five patients were treated with a HemiCAP® (N = 116 HemiCAPs®) between 2006 and 2014. Revision rates, arthrosis score, hallux valgus (HV), intermetatarsal (IM), distal metaphyseal articular angle (DMAA), visual analog scale (VAS) (1-10 points), American Orthopaedic Foot and Ankle Score (AOFAS) MTP-IP (AOFAS 0-100 points), SF-12, range of motion (ROM), and radiographs were analyzed pre- and postoperatively. Statistics: Kaplan-Meier survival analysis, Cox-regression, and paired t tests. At 2, 4, and 6 years, the implant survival was 87%, 83%, and 81%, respectively. All revised due to pain. Dorsal flange, gender, arthrosis, HV, IM, and DMAA did not influence the results. At the mean 5-year follow-up (n = 47) median (range) dorsal ROM was 45° (10°-75°), AOFAS was mean 87.2 ± 10.8, VAS was 2 ± 1.6, and SEFAS was 42 ± 6 points. The dorsal flange made no significant difference for ROM or patient-reported outcome measures compared to the HemiCAP® with no dorsal flange. Twenty-three patients with preoperative data were re-examined, and preoperative dorsal ROM mean difference (confidence interval [CI]) increased 20.7° (13.9°-27.4°), VAS decreased with a mean difference (CI) of ?4.7 (?5.8 to 3.5), and AOFAS increased with a mean difference (CI) 26.2 (20.2-32.2) (for all p < .001). The 6-year survival rate of the HemiCAP® implant was 81%. The design change to dorsal flange was not evident clinically. Unrevised patients had significantly less pain, greater ROM, and better foot and ankle function than preoperatively.     

Safety and Effectiveness of Mentor’s MemoryGel Implants at 6 Years

Background  In November 2006, the FDA approved the Premarket Approval PMA applications for the round, cohesive, silicone gel-filled breast implants of Mentor (MemoryGel) and Allergan. Since that time, the devices have been widely available to plastic surgeons and their use is rapidly eclipsing that of the saline breast implants. Patients in the Core clinical studies supporting these approvals continue to be followed through for 10 years, with comprehensive annual patient and physician-reported evaluations of safety and efficacy. Methods  One thousand and eight (1,008) female patients had data collected on 1,898 implants, and were enrolled at 48 sites. Key complication rates were recorded with Kaplan–Meier estimated cumulative incidence calculation for each. Results  Rupture rate, suspected and confirmed, for primary augmentation was 1.1% (95% CI, 0.3–4.3), and that for primary reconstruction patients was 3.8% (95% CI, 1.4–9.8). Capsular contracture rates for clinically significant Baker III/IV contracture for primary augmentation was 9.8% (95% C I, 7.6–12.7), and that for primary reconstruction was 13.7% (95% CI, 9.7–19.1). The reoperation incidence for primary augmentation and primary reconstruction was 19.4 and 33.9%, respectively, with explantation and replacement with a study device in 3.9% of primary augmentations and 10.4% of primary reconstructions. Conclusions  Mentor MemoryGel Silicone Breast implants represent a safe and effective choice for women seeking breast augmentation or breast reconstruction following mastectomy.

How Texture-Inducing Contraction Vectors Affect the Fibrous Capsule Shrinkage Around Breasts Implants?

Background  

Breast augmentation was performed on nine female volunteer patients to determine the influence of three textured surfaces on fibrous capsule formation. The high degree of surface texture reduced the capsular fibrous tissue formation.     

Histologic Analysis of Zafirlukast’s Effect on Capsule Formation Around Silicone Implants

Background The most common complication experienced by patients who have undergone mammary implant surgery is capsular contracture. This matter concerns physicians and patients, but to date, there is no effective way to avoid this complication. Surgical intervention usually is required. In 2002, the use of zafirlukast, a leukotriene inhibitor (a drug used for asthma treatment), was reported for the treatment of capsular contracture, with good results. Methods For this study, 30 female Wistar rats were used. These animals received two silicone implants each: one with a smooth surface and one with a textured surface. All the animals received daily intraperitoneal injections for 90 days and were divided as follows: control group (C) receiving only saline solution, experimental group 1 (E-I) receiving 1.25 mg/kg/day of zafirlukast, and experimental group 2 (E-II) receiving 5 mg/kg/day of zafirlukast. Histologic analysis used hematoxilin and eosin to verify vessels, capsule thickness, and inflammatory cells. Immunoistochemical analysis with smooth muscle anti-actin antibody was used for myofibroblast verification. Picro-Sirius under polarized light was used for collagen analysis. Results Textured implant experimental groups presented smaller numbers of vessels, thinner capsules, lower collagen density, and smaller numbers of mastocytes and eosinophils than the control group. No significant differences were found in smooth surface implants, as compared with the control group. Conclusion Zafirlukast reduced the occurrence of factors directly and indirectly connected with capsular contracture.     

Filling of Adjustable Breast Implants Beyond the Manufacturer’s Recommended Fill Volume

BACKGROUND: Adjustable breast implants are widely used for both reconstructive and cosmetic breast surgery. They provide unique postoperative versatility and allow for more effective management of numerous conditions that would otherwise require surgical intervention. Findings have shown that in a clinical setting, it often is necessary to overexpand saline implants beyond the manufacturer's recommended fill volumes for positive results and optimal patient satisfaction. The authors investigated their breast-augmentation patients, comparing implants expanded beyond the manufacturer's fill volume with implants that remained within the recommended parameters. METHODS: A total of 138 patients (270 implants) undergoing breast augmentation mammoplasty with Smooth Round Spectrum implants were evaluated postoperatively. To determine the effects of overexpansion, the incidence of leakage was assessed as well as the possibility of increased firmness. Patients completed a satisfaction questionnaire. RESULTS: The findings showed no evidence of increased leakage with implants expanded beyond recommended fill volumes, and 97% of the patients reported a perfect score for satisfaction ratings. Of the 270 implants evaluated in the study, only 7 were given a less than perfect score. CONCLUSIONS: By exceeding the recommended fill volume, the authors were able to use the implant to its maximal potential, with increased patient satisfaction. The authors were able to correct problems and avoid complications that could not have been resolved without deviating from the manufacturer's recommended fill volumes. Nonvalidated restrictions on fill volumes severely limit the efficacy of adjustable implants.     

Patient Retention and Replacement Trends After Saline Breast Implants: Are Deflations Inflationary?

Background  This study aimed to examine serial operative trends with patients who have experienced surgical implant deflation. In addition, the economic impact of deflation on practice caseload was analyzed. Methods  A retrospective review was conducted to examine patients who experienced deflation from 2000 to 2007. Patient demographics, implant data, and the presence of secondary (performed at explantation) or tertiary (performed later) procedures were examined. Financial information was tabulated to determine the economic multiplier effect (i.e. the expected value of revenue from secondary and tertiary procedures divided by explantation cost) of taking on deflation cases in a practice. Results  For this study, 285 patients with an average age of 38.4 years were identified. The average time to explantation was 50 months. Slightly more than half of the patients (55%) had both implants replaced at the time of explantation, whereas 59% switched to silicone implants and 41% continued with saline implants. A larger implant was chosen by 54% of the patients (average increase, 82 ml), whereas 18% underwent secondary procedures at the time of explantation including mastopexy (n = 22), facial rejuvenation (n = 8), liposuction (n = 7), or a combination of the two (n = 8). Tertiary procedures were performed for 31% of the patients after their explantation/reimplantation (average time frame, 13 months). The tertiary procedures included replacement with silicone (33.7%), liposuction (24.7%), abdominoplasty (11.2%), facial rejuvenation (13.5%), or nonsurgical rejuvenation using Botox, Restylane, or laser procedure (33.7%). Economic multiplier analysis showed that the financial impact of revenue derived from implant deflation on downstream practice revenue is 1.02. Conclusion  At the time of explantation, replacement with silicone after saline deflation is common (59% of patients). In this study, patients who chose replacement with saline had a significant tendency to replace with silicone (33%) as a tertiary procedure. Saline deflation represents a substantial opportunity for practice development. In particular, it has a positive impact on patient retention for additional aesthetic surgical or nonsurgical procedures. Economic multiplier analysis can be used to quantify the financial impact of saline deflation. Presented at The Aesthetic Meeting 2008, American Society Aesthetic Plastic Surgeons Annual Meeting, San Diego, CA, 2 May 2008.     

Are Current Total Knee Arthroplasty Implants Designed to Restore Normal Trochlear Groove Anatomy?

Biomechanical studies have shown that external rotation of the femoral TKA component improves patellar tracking but does not restore it to physiologic values. We hypothesized that this could be due to differences in the trochlear groove geometry of TKA and normal knees. This was investigated via a virtual TKA procedure that mounted femoral components on to 3-dimensional models of healthy femurs, followed by measurement of the trochlear geometry before and after the simulated TKA. The results showed that (1) external rotation of the component brought the trochlear groove closer to normal anatomy than no external rotation; (2) however, even with external rotation, the trochlear anatomy was only partially restored to normal. Further work is needed to determine implications for patellofemoral complications observed with current TKA designs.     

Femoral Neck Notching in Dual Mobility Implants: Is This a Reason for Concern?

BackgroundDual mobility (DM) total hip arthroplasty (THA) implants have been advocated for patients at risk for impingement due to abnormal spinopelvic mobility. Impingement against cobalt-chromium acetabular bearings, however, can result in notching of titanium femoral stems. This study investigated the incidence of femoral stem notching associated with DM implants and sought to identify risk factors.MethodsA multicenter retrospective study reviewed 256 modular and 32 monoblock DM components with minimum 1-year clinical and radiographic follow-up, including 112 revisions, 4 conversion THAs, and 172 primary THAs. Radiographs were inspected for evidence of femoral notching and to calculate acetabular inclination and anteversion. Revisions and dislocations were recorded.ResultsTen cases of femoral notching were discovered (3.5%), all associated with modular cylindrospheric cobalt-chromium DM implants (P = .049). Notches were first observed radiographically at mean 1.3 years after surgery (range 0.5-2.7 years). Notch location was anterior (20%), superior (60%), or posterior (20%) on the prosthetic femoral neck. Notch depth ranged from 1.7% to 20% of the prosthetic neck diameter. Eight cases with notching had lumbar pathology that can affect spinopelvic mobility. None of these notches resulted in stem fracture, at mean 2.7-year follow-up (range 1-7.6 years). There were no dislocations or revisions in patients with notching.ConclusionFemoral notching was identified in 3.5% of DM cases, slightly surpassing the dislocation rate in a cohort selected for risk of impingement and instability. Although these cases of notching have not resulted in catastrophic failures thus far, further study of clinical sequelae is warranted. Component position, spinopelvic mobility, and implant design may influence risk.     

Periprosthetic Bone Resorption and Sigmoid Notch Erosion Around Ulnar Head Implants: A Concern?

Metallic ulnar head implants have been proposed not only to solve symptomatic radioulnar impingement after Darrach or Sauvé-Kapandji procedures, but also to prevent such an impingement when treating arthritic distal radioulnar joint. This article prospectively analyzes a series of ulnar head implants with special reference to bone resorption at the prosthesis collar and erosion of the sigmoid notch of the distal radius at an average follow-up of 32 months (minimum 24 months).     

Effect of Implantation Surgery on the Strength Properties of Silastic® II Silicone Gel Breast Implants

Background: The causes of silicone gel–filled breast implant rupture are uncertain, and little research has been directed toward characterizing or quantifying the multiple factors that may contribute to device failure. Breast implants are subjected to some degree of stress and deformation during the surgical procedures of insertion. Thus implantation surgery itself could be a factor in affecting the durability of breast implants. Objective: The purpose of this study was to investigate whether the surgical procedure of insertion affects the mechanical properties of the silicone elastomer shell of gel–filled implants. We wanted to determine whether the procedure of inserting a breast implant might cause a decrease in the strength properties of the shell. Methods: Thirty-four Silastic^® II gel–filled breast implants manufactured by Dow Corning were tested. All implants were from the same lot and had a volume of 300 cc. Twenty of 34 implants were tested without implantation to investigate variability within a lot and establish a baseline of control data for comparison with implanted implants. Fourteen of the 34 implants were implanted through an inframammary incision in the right breast of a cadaver. The effect of implantation surgery was investigated by comparing the mechanical properties of the anterior and posterior sides of the cadaver explants with those of the controls. Results: Statistical analysis of the data indicated that the mechanical properties of elongation and tear resistance were essentially unaffected by implantation surgery. However, the average tensile strength of the explants was reduced 4.9% to 6.2% (for shells extracted with hexane and unextracted shells, respectively) compared with the controls. Breaking energy averages for the explants were also reduced 7.8% to 5.9% (for extracted and unextracted shells, respectively) when compared with the controls and average moduli decreased by a similar magnitude. Conclusions: The surgical procedure of implanting a breast implant has a small but statistically significant effect on the average strength properties of the elastomer shell of the implant. It is unlikely that this small reduction is sufficient to be a factor in implant durability.     

Metacarpophalangeal Joint Implants: II. Roentgenographic Study of the Niebauer™ Cutter Metacarpophalangeal Joint Prosthesis

A roentgenographic study was carried out on 41 Niebauer^T-^MCutter Metacarpophalangeal Joint Prosthesis from 1 to 36 month; postoperatively, a total of 105 examinations. The examinations were performed in the AP-projection and in the lateral projection by tomography in maximum active extension and flexion. The tomographic examinations revealed implant damage of three kinds: cracking within the midsection; fragmentation of the midsection; fracture of the hinge. Cracking within the midsection was found in 8 implants between 6 and 12 months postoperatively and in 1 implant later than 12 months. Later examinations revealed fragmentation of the midsection in 2 implants previously showing cracks. Hinge fracture was observed in 22 implants. Implant damage was found in a total frequency of 26/41. Bone reaction was found on the tomograms in all the operated joints, and could not be evaluated on the AP-projections. A bony spur was found to develop on the metacarpal bone volarly at the site of the osteotomy in 35 joints. In 2 of these the bony spur reached the base of the proximal phalanx, causing anchylosis. Bone resorption was found in 23 joints, constantly dorsally in the metacarpal bone and volarly in the proximal phalanx. The mechanism of the implant damage is discussed with respect to the shearing forces in the joint and the two materials of differing elasticity constituting the implant. The bone reaction is discussed with respect to the intended fixation of the intramedullary stems.     

Does the Additional Articulation in Retrieved Bipolar Hemiarthroplasty Implants Decrease Trunnionosis Compared to Total Hip Arthroplasty?

Background

Trunnionosis at the modular head-neck taper interface in metal-on-polyethylene total hip arthroplasty (MoP THA) has been shown to occur, and represents a potential mode of MoP THA failure. The purpose of the present investigation is to elucidate differences in fretting and corrosion at the head-neck taper interface of prostheses retrieved from bipolar hemiarthroplasty (BH) and MoP THA.

Does the Surface Structure of Implants Have an Impact on the Formation of a Capsular Contracture?

Background The formation of a fibrous capsule around a silicone breast implant is part of a physiologic foreign body reaction after breast augmentation. In contrast, the formation of a capsular contracture is a local complication of unknown cause. This study aimed to discover whether the surface structure of the implant (textured vs smooth) has any impact on the formation of a capsular contracture. Methods This prospective study included 48 female patients with unilateral capsular fibrosis grades 1 to 4 in Baker’s clinical scaling system. Of these patients, 14 received implants with a textured surface (Mentor), and 34 received implants with a smooth surface (Mentor). The implants all were placed in a submuscular position by the same experienced plastic surgeon. The clinical data were assessed using standardized patient questionnaires. For histologic diagnosis, operatively excised capsular tissue was examined. Preoperatively, venous blood samples for determining serum hyaluronan concentrations were taken from the patients. The control group consisted of 20 patients without capsular fibrosis. Results The separate analysis of clinical data for the patients with textured and those with smooth-surfaced breast implants showed a slightly reduced degree of symptoms for the patients with textured silicone breast implants, as compared with those who had smooth-surfaced implants. The histologic assessment of the fibrosis showed a symmetric distribution for Wilflingseder scores 1 to 3 (29% each), whereas 13% of the capsular tissues could be assigned to Wilflingseder score 4. In contrast, the histologic assessment of the patients with smooth-surfaced implants predominantly showed a Wilflingseder score of 3 (65%). The serologic investigations via enzyme-linked immunoassay (ELISA) showed serum hyaluronan concentrations of 10 to 57 ng/ml (25.0 ± 11.7 ng/ml). Therefore, no statistically significant differences in terms of serum hyaluronan levels could be determined between the two groups of patients. In comparison with the control group, the patients with implants showed elevated serum hyaluronan levels (p < 0.05). Conclusions The histologic examination and serum hyaluronan concentration analysis showed no statistically significant difference between smooth-surfaced and textured implants (Mentor) with respect to the development of capsular contracture. On the other hand, the severity of capsular contracture showed a positive linear correlation with the degree of local inflammatory reactions, which were independent of the implant surface.     

Tibial Tray Thickness Significantly Increases Medial Tibial Bone Resorption in Cobalt–Chromium Total Knee Arthroplasty Implants

Background

Stress shielding is an uncommon complication associated with primary total knee arthroplasty. Patients are frequently identified radiographically with minimal clinical symptoms. Very few studies have evaluated risk factors for postoperative medial tibial bone loss. We hypothesized that thicker cobalt–chromium tibial trays are associated with increased bone loss.