Limb Lengthening and Reconstruction Society AIM Index Reliably Assesses Lower Limb Deformity

Abstract Background Although several systems exist for classifying specific limb deformities, there currently are no validated rating scales for evaluating the complexity of general lower limb deformities. Accurate assessment of the complexity of a limb deformity is essential for successful treatment. A committee of the Limb Lengthening and Reconstruction Society (LLRS) therefore developed the LLRS AIM Index to quantify the severity of a broad range of lower extremity deformities in seven domains. Questions/Purposes We addressed two questions: (1) Does the LLRS AIM Index show construct validity by correlating with rankings of case complexity? (2) Does the LLRS AIM Index show sufficient interrater and intrarater reliabilities? Methods We had eight surgeons evaluate 10 fictionalized patients with various lower limb deformities. First, they ranked the cases from simplest to most complex, and then they rated the cases using the LLRS AIM Index. Two or more weeks later, they rated the cases again. We assessed reliability using the Kendall's W test. Results Raters were consistent in their rankings of case complexity (W = 0.33). Patient rankings also correlated with both sets of LLRS AIM ratings (r 2 = 0.25; r 2 = 0.23). The LLRS AIM Index showed interrater reliability with an intraclass correlation (ICC) of 0.97 for Trial 1 and 0.98 for Trial 2 and intrarater reliability with an ICC of 0.94. The LLRS AIM Index ratings also were highly consistent between the attending surgeons and surgeons-in-training (ICC = 0.91). Conclusions Our preliminarily observations suggest that the LLRS AIM Index reliably classifies the complexity of lower limb deformities in and between observers

Pin-track infections: Past, present, and future

Pin-track infections are a common problem with external fixation and any other implant that breaks the skin barrier. The literature is rich with reports and techniques for treating these infections, but lacks a universally accepted definition of a pin track infection, a single commonly accepted classification, or a standard method of reporting. However, the surgeon can follow a commonly accepted series of practical steps to reduce the occurrence of infection. Continuing development of improved surfaces, substances, and techniques may make pin track infections rarer in the future. Careful preoperative planning, meticulous surgical technique, patient education, and close patient monitoring are all critical to minimize pin-track infections

A systematic review of incidence of pin track infections associated with external fixation

Depending on the reference, pin track infection rates in external fixation surgery have been stated to be anywhere from 0% to 100%. We critically evaluated the pin track infection rate for external fixation by performing systematic review of the external fixation literature since 1980. Using PubMed, a search of the peer-reviewed literature on external fixation was performed. This systematic review was conducted, as much as possible, in accordance with PICOS and PRISMA guidelines. A total of 150 articles were reviewed, including at least one from each year between 1980 and 2014. The following data were collected from each article: the year of publication, number of patients in the study, average age of the patients, reason for the external fixation, fixation per segment (two or more than two points), body part involved, whether or not hydroxyapatite-coated pins were used, duration of the external fixator, type of fixator used, and number of patients with documented pin track infections. These 150 studies represented 6130 patients. There were 1684 reported pin track infections from these 6130 patients, giving a cumulative pin track infection rate of 27.4%. A more recent year of publication was associated with an increasing infection rate (P = 0.015) while increasing age was associated with a decreased infection rate (P < 0.0005). There were trends toward association of humerus location (P = 0.059), shorter fixator duration (P = 0.056), and circular fixation (P = 0.079) with decreased infection rates. This systematic review of external fixation publications revealed a cumulative pin track infection rate of 27%. Younger age was the factor leading to increased pin track infection rates. Circular fixation trended toward being protective of pin track infection when usage was factored into the multiple regression analysis. Longer duration of fixation trended toward increased infection rate as expected. This data provides important base values for a common complication in external fixation treatment, highlights the importance of a more consistent definition of a pin track infection in future research, and identifies the pediatric population as the group at greatest risk

Determining When It Is Safe To Remove The External Fixator: Results From A Survey Of The Limb Lengthening And Reconstruction Society

Thousands of external fixators are applied for distraction osteogenesis each year. Determining when it is safe to remove the fixator can be difficult. The purpose of this study was to survey an international group of external fixation surgeons to determine their current practice patterns surrounding external fixator removal. A 10-question, open-ended survey was emailed to members of the Limb Lengthening and Reconstruction Society. Responses were recorded, and statistical analysis was performed. Pearson\u27s chi-square test and likelihood ratio were used when indicated. A total of 124 surveys were sent, and 44 responses were received (35% response rate). The top 5 responses for determining when it is safe to remove a fixator were full weight bearing (75%), 3 cortices (71%), no pain (55%), after dynamization (55%), and duration of time (30%). Forty-eight percent of respondents routinely dynamized the frame prior to removal. Significantly fewer surgeons who dynamized the frame protected the limb after removal (P=.046). Physicians who dynamized the frame tended to use a less-constricting device for protection (boot or brace vs cast) than those who did not dynamize (P=.016). This study showed that most surgeons used radiographs and clinical evaluation to determine timing of fixator removal. Only 23% reported using computed tomography. Most surgeons dynamized the fixator prior to removal. Those who dynamized the frame were more confident in the regenerate healing. Although this study offers insight into what experienced surgeons do in their daily practice, it reveals many areas for improvement in the literature

A comparison of deformity correction capabilities in hexapod frame systems

Context: Hexapod fixators can be divided into two basic design groups. One group consists of frames that use ball and socket joint struts attached to the outer surface of the rings. The other group consists of frames that use cardan type universal joint struts attached to the under surface of the rings. Aims: To compare the ability of different hexapod fixator systems for deformity correction. Settings and Design: Nearly, identical two-ring frame constructs were compared to determine if there was any difference in deformity correction capability between cardan type universal joint struts and ball and socket joint struts. Materials and Methods: Maximal deformity was created using the software for each of the frame constructs in all six planes of deformity (angulation, translation, and rotation in the coronal and sagittal planes). Clinical scenarios were also compared (equinus contracture, moderate Blount disease, and severe Blount disease) and the number of strut changes necessary to correct the deformity were recorded. Results: For the small and medium-sized struts, the angular deformity corrections were similar, but the cardan type universal hinges had a greater capability for correcting translational deformity and rotation than the ball and socket joints. However, the amount of lengthening possible was greater for the ball and socket joints with these strut sizes. In the largest size of struts, the ball and socket joints had greater range in every category except rotation. In patients requiring significant rotational correction, the cardan type universal joints were found to impinge on the soft tissues 13° earlier than the ball and socket joints (39° vs. 52°). A Blount disease case with moderate multiplanar deformity and an equinus correction of 45° required the same amount of strut changes for each design. For the Blount disease case with severe multiplanar deformity, the cardan type universal joint struts required six total changes, whereas the ball and socket joint struts required only one strut change and two strut adjustments to achieve the same correction. Conclusions: Both the cardan type universal joint and the ball and socket joint hexapod frame designs allow substantial multiplanar corrections to occur. In the smaller size struts, the cardan type universal joints allow more translation and rotation, whereas the ball and socket joints allow more length. For large rotational corrections and frames built with 90° of offset, the ball and socket joint design is better at avoiding soft tissue impingement. While both systems are comparable with mild to moderate deformity correction, the ball and socket joint design allows more correction with less strut changes for patients with severe deformity in our experimental construct

Analysis of strut-to-bone lengthening ratio for hexapod frames using mathematical modeling

Background: Hexapod external fixators often incorporate bone lengthening as part of a multi-planar deformity correction plan. The hexapod struts, however, do not distract in the direction of bone lengthening. Their oblique orientation to the ring creates a vector that is the summation of multiple individual strut adjustments. We demonstrate that a 1 mm lengthening of each of all six struts always created more than 1 mm of lengthening at the bone. Methods: The amount of lengthening was analyzed with the Taylor Spatial Frame™ (Smith and Nephew, Memphis, TN, USA) software using two different methods. Results: As the strut lengths got longer the ratio got closer to one but it never reached 1.0. Conclusions: This information is critical when using very short struts or very large rings. In these two scenarios, the Δ frame height relative to the Δ strut length becomes much greater than one. Clinical Relevance: A strut length much greater than one will cause the bone to lengthen much faster than the surgeon desires. It may also lead to unhealthy regenerate bone formation and could create delays in bone healing

Determining When It Is Safe to Remove the External Fixator: Results From a Survey of the Limb Lengthening and Reconstruction Society

Thousands of external fixators are applied for distraction osteogenesis each year. Determining when it is safe to remove the fixator can be difficult. The purpose of this study was to survey an international group of external fixation surgeons to determine their current practice patterns surrounding external fixator removal. A 10-question, open-ended survey was emailed to members of the Limb Lengthening and Reconstruction Society. Responses were recorded, and statistical analysis was performed. Pearson\u27s chi-square test and likelihood ratio were used when indicated. A total of 124 surveys were sent, and 44 responses were received (35% response rate). The top 5 responses for determining when it is safe to remove a fixator were full weight bearing (75%), 3 cortices (71%), no pain (55%), after dynamization (55%), and duration of time (30%). Forty-eight percent of respondents routinely dynamized the frame prior to removal. Significantly fewer surgeons who dynamized the frame protected the limb after removal (P=.046). Physicians who dynamized the frame tended to use a less-constricting device for protection (boot or brace vs cast) than those who did not dynamize (P=.016). This study showed that most surgeons used radiographs and clinical evaluation to determine timing of fixator removal. Only 23% reported using computed tomography. Most surgeons dynamized the fixator prior to removal. Those who dynamized the frame were more confident in the regenerate healing. Although this study offers insight into what experienced surgeons do in their daily practice, it reveals many areas for improvement in the literature

Plate-assisted Lengthening of the Femur and Tibia in Pediatric Patients.

BACKGROUND: Limb lengthening over a percutaneous plate can be used during pediatric distraction osteogenesis to decrease the time of external fixation. METHODS: A retrospective, consecutive 2-surgeon experience of pediatric femoral and tibial lengthenings with a plate-assisted lengthening (PAL) technique was performed. The plate was placed at the time of index corticotomy. The primary outcome measures of external fixation index, consolidation index, and complications were assessed for each lengthening. RESULTS: From 2005 to 2012, 38 lengthenings (23 femur, 15 tibia) in 30 patients were performed by a PAL technique. All patients experienced successful distraction and consolidation. The average achieved lengthening was 3.80±0.98 cm (range, 2.2 to 6.4) with an average consolidation index of 27 days/cm and a mean external fixation index of 13.1±4.29 days/cm (range, 7.8 to 30). Patients returned to full weight-bearing activity after an average of 98.3±28.5 days. There were an average of 1.08±1.05 total complications and 0.39±0.75 severe complications per lengthening. Complications were encountered most commonly during femoral lengthening, including procurvatum and varus deformity through the regenerate. These deformities were usually corrected by frame adjustment before removal. CONCLUSIONS: PAL is a safe technique that minimizes time of external fixation, accelerates rehabilitation and weight-bearing, and can be successfully used on the femur or tibia. The most common complications are angular deformities of the regenerate that can be treated with adjustment before or at the time of plate locking. LEVEL OF EVIDENCE: Level IV-retrospective case series