Surgical aspects of the diabetic foot

Assessment of bone marrow edema on dual-energy CT scans in people with diabetes mellitus and suspected Charcot neuro-osteoarthropathy

OBJECTIVE

This study aimed to quantitatively assess the diagnostic value of bone marrow edema (BME) detection on virtual non-calcium (VNCa) images calculated from dual-energy CT (DECT) in people with diabetes mellitus and suspected Charcot neuro-osteoarthropathy (CN).

MATERIALS AND METHODS

People with diabetes mellitus and suspected CN who underwent DECT of the feet (80kVp/Sn150kVp) were included retrospectively. Two blinded observers independently measured CT values on VNCa images using circular regions of interest in five locations in the midfoot (cuneiforms, cuboid and navicular) and the calcaneus of the contralateral or (if one foot was available) the ipsilateral foot. Two clinical groups were formed, one with active CN and one without active CN (no-CN), based on the clinical diagnosis.

RESULTS

Thirty-two people with diabetes mellitus and suspected CN were included. Eleven had clinically active CN. The mean CT value in the midfoot was significantly higher in the CN group (-55.6 ± 18.7 HU) compared to the no-CN group (-94.4 ± 23.5 HU; p < 0.001). In the CN group, the difference in CT value between the midfoot and calcaneus was statistically significant (p = 0.003); this was not the case in the no-CN group (p = 0.357). The overall observer agreement was good for the midfoot (ICC = 0.804) and moderate for the calcaneus (ICC = 0.712). Sensitivity was 100.0% and specificity was 71.4% using a cutoff value of -87.6 HU.

CONCLUSION

The detection of BME on VNCa images has a potential value in people with diabetes mellitus and suspected active CN.

Use of in vitro bone models to screen for altered bone metabolism, osteopathies, and fracture healing: challenges of complex models

Approx. every third hospitalized patient in Europe suffers from musculoskeletal injuries or diseases. Up to 20% of these patients need costly surgical revisions after delayed or impaired fracture healing. Reasons for this are the severity of the trauma, individual factors, e.g, the patients’ age, individual lifestyle, chronic diseases, medication, and, over 70 diseases that negatively affect the bone quality. To investigate the various disease constellations and/or develop new treatment strategies, many in vivo, ex vivo, and in vitro models can be applied. Analyzing these various models more closely, it is obvious that many of them have limits and/or restrictions. Undoubtedly, in vivo models most completely represent the biological situation. Besides possible species-specific differences, ethical concerns may question the use of in vivo models especially for large screening approaches. Challenging whether ex vivo or in vitro bone models can be used as an adequate replacement for such screenings, we here summarize the advantages and challenges of frequently used ex vivo and in vitro bone models to study disturbed bone metabolism and fracture healing. Using own examples, we discuss the common challenge of cell-specific normalization of data obtained from more complex in vitro models as one example of the analytical limits which lower the full potential of these complex model systems.

Pé diabético. Parte 1: Úlceras e Infecções*

Diabetes is a systemic disease that has achieved epidemic proportions in modern society. Ulcers and infections are common complications in the feet of patients with advanced stages of the disease, and are the main cause of amputation of the lower limb. Peripheral neuropathy is the primary cause of loss of the protective sensation of the feet and frequently leads to plantar pressure ulcers and osteoarticular disruption, which in turn develops into Charcot neuropathy (CN). Common co-factors that add to the morbidity of the disease and the risk of amputation in this population are obesity, peripheral arterial disease, immune and metabolic disorders. Orthopedic surgeons must be aware that the early detection and prevention of these comorbidities, through diligent medical care and patient education, can avoid these amputations.

Diabetic Foot. Part 2: Charcot Neuroarthropathy

Charcot neuroarthropathy (CN) is an unfortunate and common complication of patients with diabetes, most likely resulting from a lack of proper understanding of the disease, which leads to late diagnosis. It is commonly misdiagnosed as infection and treated with antibiotics and a frustrated attempt of surgical drainage, which will reveal only debris of the osteoarticular destruction. Proper education of diabetic patients and of the health care professionals involved in their treatment is essential for the recognition of the initial signs of CN. The general orthopedic surgeon is usually the first to treat these patients in the early stages of the disease and must be aware of the signs of CN in order to establish an accurate diagnosis and ensure proper treatment. In theory, this would make it possible to decrease the morbidity of this condition, as long as proper treatment is instituted early.

Charcot foot reconstruction outcomes: A systematic review

BACKGROUND

Charcot neuroarthropathy is a complex condition characterised by progressive deformity, limited treatment options and a high amputation rate. Surgical reconstruction of Charcot foot has been proposed as a method to preserve the foot. However, limited information exists on the different methods of reconstruction available, their outcomes and complications.

METHODS

We systematically analysed published data from Jan 1993 to Dec 2018 to assess methods of fixation and associated outcomes for the surgical reconstruction in Charcot neuroarthropathy. Statistical analyses were undertaken to determine the amputation rates, return to ambulation and complications associated with these techniques.

RESULTS

A total of 1116 feet (1089 patients) were reported to have undergone reconstruction with significant heterogeneity in patient selection. Of these, 726 (65%) were reported to undergo internal fixation, 346 feet (31%) external fixation and 44 (4%) undergoing simultaneous internal and external fixation. No single technique demonstrated a significant benefit over the other. Overall, the bone fusion rate was 86.1%. Complications directly attributable to the technique employed were noted in 36% of individuals. The reported post-reconstruction amputation rate was only 5.5% with 91% apparently returning to ambulation.

CONCLUSIONS

Although no preferential method of fixation was identified, we find that the current options for surgical reconstruction could offer limb salvage with a low amputation risk in a highly selected population. However, the lack of controlled studies, inconsistent reporting of outcomes and heterogeneity of patient selection mean that the quality of evidence is low.

The Charcot foot: a pictorial review

Charcot foot refers to an inflammatory pedal disease based on polyneuropathy; the detailed pathomechanism of the disease is still unclear. Since the most common cause of polyneuropathy in industrialized countries is diabetes mellitus, the prevalence in this risk group is very high, up to 35%. Patients with Charcot foot typically present in their fifties or sixties and most of them have had diabetes mellitus for at least 10 years. If left untreated, the disease leads to massive foot deformation. This review discusses the typical course of Charcot foot disease including radiographic and MR imaging findings for diagnosis, treatment, and detection of complications.

Corneal Subbasal Nerve Plexus Changes in Severe Diabetic Charcot Foot Deformity: A Pilot Study in Search for a DNOAP Biomarker

INTRODUCTION

Diabetic neuroosteoarthropathy (DNOAP) early symptoms are unspecific, mimicking general infectious symptoms and rendering a diagnosis challenging. Consequently, unfavourable outcomes occur frequently, with recurrent foot ulceration, infectious complications, and eventually amputation. Corneal confocal microscopy (CCM) of the subbasal nerve plexus (SNP) is used to detect early peripheral neuropathy in diabetic patients without diabetic retinopathy. This pilot study was designed to determine if specific SNP changes manifest in severe DNOAP in comparison to a healthy control group.

METHODS

This pilot study utilized a matched-pair analysis to investigate SNP changes by in vivo CCM for 26 patients (mean patient age 63.7 years, range 27 to 78) with severe DNOAP defined by condition after the need for reconstructive foot surgery (n = 13) and a healthy control group (n = 13). Corneal nerve fibre length (CNFL), nerve fibre density (CNFD), nerve branch density (CNBD), average weighted corneal nerve fibre thickness (CNFTh), nerve connecting points (CNCP), and average weighted corneal nerve fibre tortuosity (CNFTo) were assessed as well as the general clinical status, diabetic status, and ophthalmologic basic criteria.

RESULTS

In vivo CCM revealed significantly reduced SNP parameters in the DNOAP group for CNFL (p = 0.010), CNFD (p = 0.037), CNBD (p = 0.049), and CNCP (p = 0.012) when compared to the healthy control group. Six patients (46%) of the DNOAP group suffered from diabetic retinopathy and none of the control group.

CONCLUSIONS

This pilot study revealed a rarefication of SNP in all measured parameters in patients with severe DNOAP. We see a potential value of CCM providing a SNP-based biomarker for early stages of DNOAP prior to the development of any foot deformities that needs to be evaluated in further studies. This trial is registered with German Clinical Trials Register (DKRS) DRKS00007537.

Surgical Treatment Options for the Diabetic Charcot Hindfoot and Ankle Deformity

Charcot neuroarthropathy is associated with progressive, noninfectious, osteolysis-induced bone and joint destruction. When the ankle and/or hindfoot is affected by the destruction process, management is further complicated with collapse and destruction of the talar body, which increases instability around the ankle. In this patient population, arthrodesis is the most commonly used surgical procedure. Internal fixation, external fixation, or a combination of both can be used for the treatment. Decision making between them should be individualized according to the patient characteristics.

Lower Extremity Amputation and Mortality Rates in the Reconstructed Diabetic Charcot Foot and Ankle With External Fixation: Data Analysis of 116 Patients

The aim of this study was to determine the lower extremity amputation and mortality rates of a group of patients who underwent reconstructive surgery using circular external fixation for treatment of diabetic Charcot neuroarthropathy (CN) of the foot and/or ankle. Existing studies regarding lower extremity amputation or mortality rates for diabetic CN of the foot and/or ankle have been performed on mostly conservatively treated patients. The objective of the statistical analysis in this studied population was to understand the difference in overall amputation and mortality rates between the 2 main groups: one with foot and/or ankle ulceration (group 1), and the other without ulceration or osteomyelitis (group 2, control group). Within group 1, 2 subgroups were established: one with osteomyelitis (group 1A) and the other without osteomyelitis (group 1B). Initially, a retrospective analysis of 150 consecutive surgically reconstructed diabetic foot and ankle cases using circular external fixation from January 2005 through December 2012 was conducted. Those which were not supported with the diagnosis of diabetic CN were excluded and the 2 other charts without proper follow-up duration (6 months) for analysis were removed, resulting in the final sample size of N = 116. There were a total of n = 7 (6.0%) below the knee amputations (group 1A = 1, group 1B = 4, and group 2 = 2) with a total of n = 5 mortalities (4.3%) (group 1A = 2, group 1B = 2, and group 2 = 1). The total amount of time for a lower extremity amputation event (n = 7) since the time of surgical reconstruction was 729.43 ± 519.73 days (range 230-1777 days) while for a mortality event (n = 5), it was 1302.00 ± 765.48 days (range 633-2499 days).

LEVELS OF EVIDENCE

Prognostic, Level III: Retrospective study.

Prediction of complications in a high-risk cohort of patients undergoing corrective arthrodesis of late stage Charcot deformity based on the PEDIS score

Background

All diabetic neuroosteoarthropathy (Charcot arthropathy) treatment concepts are focused on a long-term infection-free, ulcer-free, and plantigrade sufficiently stable foot in order to avoid amputation. Reconstructive arthrodesis techniques for severe deformities are associated with high postoperative complication rates. This study reports a detailed complication analysis and provides a strategy that may help detect patients at risk for a complicated postoperative course.

Methods

The study comprised 43 feet in 37 patients with severe non-plantigrade or unstable Charcot deformity, Eichenholtz stages II/III (Sanders and Frykberg types II-V), who underwent reconstructive arthrodesis of the mid- and/or hindfoot. Patients were retrospectively enrolled 4.5 years postoperatively (range 1.8–11.2 years). All patients showed at least two out of five positive Pinzur high-risk criteria (immuno-compromising illnesses, large bone deformity, longstanding ulcer overlying infected bone, regional osteopenia, obesity). Follow-up included a detailed clinical analysis and radiologic assessment with emphasis on complication analysis and evaluation in accordance to the PEDIS classification system.

Results

Significantly lower overall complication rates, as well as re-operation, reulceration and amputation counts were found for patients with a cumulative PEDIS count below 7. For PEDIS single criteria, significantly lower overall complication rates were found for patients without signs of occlusive peripheral artery disease, an ulcer extent <0.9 cm², ulcer depth including erosion and inflammation of the skin and subcutaneous tissues only. Soft-tissue complications affected 49 % of patients, hardware breakage 33 %, hardware loosening 19 %, non-union 18 % and amputation 21 %. Radiographs revealed a correct reconstruction and restoration of all foot axes postoperatively with partial recollapse at the lateral foot column; however, fixation strength for the medial column was maintained.

Conclusions

Internal corrective arthrodesis for patients within the deformed stages of Charcot deformity can provide adequate reconstruction, as assessed by intraoperative radiographic measures, that exhibit superior long-term stability for the medial column. Despite a high risk patient population, a favourable outcome in terms of overall complication, re-ulceration, and amputation rates for patients/feet with a cumulative PEDIS count below 7 was found. The cut-off value of 7 may aid clinical decision-making during preoperative planning for Charcot deformity.

The medial column Synthes Midfoot Fusion Bolt is associated with unacceptable rates of failure in corrective fusion for Charcot deformity: Results from a consecutive case series

Charcot neuro-osteoarthropathy (CN) of the midfoot presents a major reconstructive challenge for the foot and ankle surgeon. The Synthes 6 mm Midfoot Fusion Bolt is both designed and recommended for patients who have a deformity of the medial column of the foot due to CN. We present the results from the first nine patients (ten feet) on which we attempted to perform fusion of the medial column using this bolt. Six feet had concurrent hindfoot fusion using a retrograde nail. Satisfactory correction of deformity of the medial column was achieved in all patients. The mean correction of calcaneal pitch was from 6° (-15° to +18°) pre-operatively to 16° (7° to 23°) post-operatively; the mean Meary angle from 26° (3° to 46°) to 1° (1° to 2°); and the mean talometatarsal angle on dorsoplantar radiographs from 27° (1° to 48°) to 1° (1° to 3°). However, in all but two feet, at least one joint failed to fuse. The bolt migrated in six feet, all of which showed progressive radiographic osteolysis, which was considered to indicate loosening. Four of these feet have undergone a revision procedure, with good radiological evidence of fusion. The medial column bolt provided satisfactory correction of the deformity but failed to provide adequate fixation for fusion in CN deformities in the foot. In its present form, we cannot recommend the routine use of this bolt.

A Guide to Improving the Care of Patients with Fragility Fractures, Edition 2

Over the past 4 decades, much has been learned about the pathophysiology and treatment of osteoporosis, the prevention of fragility fractures, and the perioperative management of patients who have these debilitating injuries. However, the volume of published literature on this topic is staggering and far too voluminous for any clinician to review and synthesize by him or herself. This manuscript thoroughly summarizes the latest research on fragility fractures and provides the reader with valuable strategies to optimize the prevention and management of these devastating injuries. The information contained in this article will prove invaluable to any health care provider or health system administrator who is involved in the prevention and management of fragility hip fractures. As providers begin to gain a better understanding of the principles espoused in this article, it is our hope that they will be able to use this information to optimize the care they provide for elderly patients who are at risk of or who have osteoporotic fractures.

Late corrective arthrodesis in nonplantigrade diabetic charcot midfoot disease is associated with high complication and reoperation rates

INTRODUCTION

Charcot arthropathy may lead to a loss of osteoligamentous foot architecture and consequently loss of the plantigrade alignment. In this series of patients a technique of internal corrective arthrodesis with maximum fixation strength was provided in order to lower complication rates.

MATERIALS/METHODS

21 feet with severe nonplantigrade diabetic Charcot deformity Eichenholtz stages II/III (Sanders/Frykberg II/III/IV) and reconstructive arthrodesis with medial and additional lateral column support were retrospectively enrolled. Follow-up averaged 4.0 years and included a clinical (AOFAS score/PSS), radiological, and complication analysis.

RESULTS

A mean of 2.4 complications/foot occurred, of which 1.5/foot had to be solved surgically. 76% of feet suffered from soft tissue complications; 43% suffered hardware-associated complications. Feet with only 2 out of 5 high risk criteria according to Pinzur showed significantly lower complication counts. Radiographs revealed a correct restoration of all foot axes postoperatively with superior fixation strength medially.

CONCLUSION

Late corrective arthrodesis with medial and lateral column stabilization in the nonplantigrade stages of neuroosteoarthropathy can provide reasonable reconstruction of the foot alignment. Nonetheless, overall complication/reoperation rates were high. With separation into low/high risk criteria a helpful guide in treatment choice is provided. This trial is registered with German Clinical Trials Register (DRKS) under number DRKS00007537.

Tibiocalcaneal Fusion for Charcot Ankle With Severe Talar Body Loss: Case Report and a Review of the Surgical Literature

Severe bone loss resulting from talar body necrosis in the Charcot ankle can be challenging to treat. In particular, the Charcot ankle will demonstrate progressive instability and deformity, causing protrusion of the medial or lateral malleolus, which will mostly lead to skin ulcers or osteomyelitis and, in some cases, will ultimately require transtibial amputation. Problems such as bone fragility, poor compliance with load-bearing restrictions, susceptibility to infection, and circulatory disorders cause difficulties in the surgical treatment of the Charcot ankle. We believe that tibiocalcaneal fusion is a reliable method to obtain satisfactory outcomes in these difficult cases. However, no study has reported on the use of a locking plate for tibiocalcaneal fusion. Therefore, we report on tibiocalcaneal fusion using a locking plate in 3 patients with Charcot ankle and severe talar body loss. All patients achieved bony union with a plantigrade foot and without any skin complications. We have concluded that a locking plate provides rigid fixation and easier insertion of additional screws, when necessary.

Primary closure of elective toe amputations in the diabetic foot--is it safe?

BACKGROUND

Toe amputation is the most common partial foot amputation. Controversy exists regarding whether to primarily close toe amputations or to leave them open for secondary healing. The purpose of this study was to evaluate the results of closed toe amputations in diabetic patients, with respect to wound healing, complications, and the need for further higher level amputation.

METHODS

We retrospectively reviewed the results of 40 elective or semi-elective toe amputations with primary closure performed in 35 patients treated in a specialized diabetic foot unit. Patients with abscesses or necrotizing fasciitis were treated emergently and were excluded. Patients in whom clean margins could not be achieved due to extensive cellulitis or tenosynovitis and patients requiring vascular intervention were excluded as well. Outcome endpoints included wound healing at 3 weeks, delayed wound healing, or subsequent higher level amputation.

RESULTS

Out of 40 amputations, 38 healed well. Thirty amputations healed by the time of stitch removal at 3 weeks and eight had delayed healing. In two patients the wounds did not heal and subsequent higher level amputation was eventually required.

CONCLUSIONS

In carefully selected diabetic foot patients, primary closure of toe amputations is a safe surgical option. We do not recommend primary closure when infection control is not achieved or in patients requiring vascular reconstruction. Careful patient selection, skillful assessment of debridement margins and meticulous technique are required and may be offered by experienced designated surgeons in a specialized diabetic foot unit.

Diabetes mellitus: musculoskeletal manifestations and perioperative considerations for the orthopaedic surgeon

Diabetes mellitus is a disease of uncontrolled hyperglycemia. Despite a more sophisticated understanding of the pathophysiology of diabetes mellitus and despite pharmacologic advancements that enable better glycemic control, the prevalence of this disease and its devastating sequelae continue to rise. The adverse effects of diabetes on the nervous, vascular, and immune systems render the musculoskeletal system vulnerable to considerable damage. Foot involvement has traditionally been thought of as the most severe and frequently encountered orthopaedic consequence. However, the upper extremity, spine, and muscles are also commonly affected. Orthopaedic surgeons are more involved than ever in the care of patients with diabetes mellitus, and they play a vital role in the multidisciplinary approach used to treat these patients. As a result, surgeons must have a comprehensive understanding of the musculoskeletal manifestations and perioperative considerations of diabetes in order to most effectively care for patients with diabetes mellitus.

Intramedullary medial column support with the Midfoot Fusion Bolt (MFB) is not sufficient for osseous healing of arthrodesis in neuroosteoarthropathic feet

INTRODUCTION

To address midfoot instability of Charcot disease a promising intramedullary implant has recently been developed to allow for an arthrodesis of the bones of the medial foot column in an anatomic position. We report on a group of patients with Charcot arthropathy and instability at the midfoot where the Midfoot Fusion Bolt had been employed as an implant for the reconstruction of the collapsed medial foot column.

MATERIAL AND METHODS

A total of 7 patients (median age 56.3 years, range 47-68) were enrolled with severe Charcot deformation at Eichenholtz stages I-II (Sanders and Frykberg types II and III). The medial column was stabilised primarily with an intramedullary rod (Midfoot Fusion Bolt) in stand-alone technique in order to reconstruct the osseous foot geometry. The bolt was inserted in a retrograde mode via the head of MTI and forwarded into the talus. Follow-up time averaged 27 months (range 9-30).

RESULTS

Intraoperative plantigrade reconstruction and restoration of the anatomic foot axes of the medial column was achieved in all cases with the need for revision surgery in 6 out of 7 patients due to soft tissue problems (2 impaired wound healing, 1 postoperative haematoma, 3 early infection). Implant-associated problems were seen in one case intra-operatively with fracture of the first metatarsal shaft and two cases with implant loosening of the MFB and need for implant removal during long time follow-up. Two patients underwent lower leg amputation due to a progressive deep soft tissue infection. One patient healed uneventfully without need for revision surgery. Except for one case recurrent ulcerations were not observed, so far.

CONCLUSION

Medial column support in midfoot instability of Charcot arthropathy with a single intramedullary rod does not provide enough stability to achieve osseous fusion. MFB loosening was associated with deep infection in a majority of our cases. To prevent early loosening of the intramedullary rod and to increase rotational stability, additional implants as angular stable plates are needed at the medial column and eventually an additional stabilisation of the lateral foot column where manifest instability exists at the time of primary surgical intervention.

Solid bolt fixation of the medial column in Charcot midfoot arthropathy

Charcot medial column and midfoot deformities are associated with rocker bottom foot, recurrent plantar ulceration, and consequent infection. The primary goal of surgical intervention is to realign and stabilize the plantar arch in a shoe-able, plantigrade alignment. Different fixation devices, including screws, plates, and external fixators, can be used to stabilize the Charcot foot; however, each of these methods has substantial disadvantages. To assess the effectiveness of rigid, minimally invasive fixation of the medial column and midfoot, 8 cases of solid intramedullary bolt fixation for symptomatic Charcot neuroarthropathy were reviewed. The patients included 6 males (75%) and 2 females (25%), with a mean age of 63 (range 46 to 80) years. The Charcot foot deformity was caused by diabetic neuropathy in 7 cases (87.5%) and alcoholic neuropathy in 1 (12.5%). The mean duration of postoperative follow-up period was 27 (range 12 to 44) months. The mean radiographic correction of the lateral talar-first metatarsal angle was 15° (range 3° to 19°), and the mean radiographic correction of the dorsal midfoot dislocation was 9 (range -4 to 23) mm. The mean loss of correction of the lateral talar-first metatarsal angle and midfoot dislocation after surgery was 7° (range 0° to 26°) and 1 (range 0 to 7) mm, respectively. No bolt breakage was observed, and no cases of recurrent or residual ulceration occurred during the observation period. Bolt removal was performed in 3 cases (37.5%), 2 (25%) because of axial migration of the bolt into the ankle joint and 1 (12.5%) because of infection. The results of the present review suggest that a solid intramedullary bolt provides reasonable fixation for realignment of the medial column in cases of Charcot neuroarthropathy.

Surgical management of Charcot neuroarthropathy of the foot and ankle: a systematic review

BACKGROUND

Charcot neuroarthropathy (CN) of the foot and ankle is an extremely challenging clinical dilemma and surgical management can be highly complicated. The current literature on this topic is comprised of manuscripts that are retrospective case series and expert opinions. Furthermore, surgery in patients with CN of the foot and ankle is guided by studies with low levels of evidence to support our current surgical practices.

METHODS

A Medline/CINAHL search was performed and a systematic review of articles discussing the surgical management of CN was undertaken.

RESULTS

Ninety-five articles fit the inclusion criteria for our study. As hypothesized, all reports detailing the surgical management of Charcot neuroarthropathy constituted Level IV or V evidence.

CONCLUSION

Surgical algorithms for the treatment of CN of the foot are based almost entirely on level four or five evidence. Uncontrolled retrospective case series and case reports guide the use of exostectomy, fusion, and Achilles tendon lengthening for CN. There is inconclusive evidence concerning timing of treatment and use of different fixation methods. Prospective series and randomized studies, albeit difficult to perform, are necessary to support and strengthen current practice.

Evolving techniques in foot and ankle amputation

Multiple clinical pathways lead to lower extremity amputation, including trauma, dysvascular disease, congenital defects, and malignancy. However, the principles of successful amputation-careful preoperative planning, coordination of a multidisciplinary team, and good surgical technique-remain the same. Organized rehabilitation and properly selected prostheses are integral components of amputee care. In the civilian setting, amputation is usually performed as a planned therapy for an unsalvageable extremity, not as an emergency procedure. The partial loss of a lower limb often represents a major change in a person's life, but patients should be encouraged to approach amputation as the beginning of a new phase of life and not as the culmination of previous treatment failures.