Introduction

Quality measures play a substantial role in the Centers for Medicare and Medicaid Services' hospital payment and public reporting programs. The purpose of this study was to assess whether public measurement of total hip and knee arthroplasty risk-standardized readmission (RSRRs) and complication rates (RSCRs) was temporally associated with decreasing rates of adverse outcomes among Medicare beneficiaries.

Recently, the use of metal-on-metal articulations in total hip arthroplasty (THA) has led to an increase in adverse events owing to local soft-tissue reactions from metal ions and wear debris. While the majority of these implants perform well, it has been increasingly recognised that a small proportion of patients may develop complications secondary to systemic cobalt toxicity when these implants fail. However, distinguishing true toxicity from benign elevations in cobalt ion levels can be challenging.

The purpose of this two part series is to review the use of cobalt alloys in THA and to highlight the following related topics of interest: mechanisms of cobalt ion release and their measurement, definitions of pathological cobalt ion levels, and the pathophysiology, risk factors and treatment of cobalt toxicity. Historically, these metal-on-metal arthroplasties are composed of a chromium-cobalt articulation.

The release of cobalt is due to the mechanical and oxidative stresses placed on the prosthetic joint. It exerts its pathological effects through direct cellular toxicity.

This manuscript will highlight the pathophysiology of cobalt toxicity in patients with metal-on-metal hip arthroplasties.

Take home message: Patients with new or evolving hip symptoms with a prior history of THA warrant orthopaedic surgical evaluation. Increased awareness of the range of systemic symptoms associated with cobalt toxicity, coupled with prompt orthopaedic intervention, may forestall the development of further complications.

Cite this article: Bone Joint J 2016;98-B:6–13.

As adverse events related to metal on metal hip arthroplasty have been better understood, there has been increased interest in toxicity related to the high circulating levels of cobalt ions. However, distinguishing true toxicity from benign elevations in cobalt levels can be challenging. The purpose of this review is to examine the use of cobalt alloys in total hip arthroplasty, to review the methods of measuring circulating cobalt levels, to define a level of cobalt which is considered pathological and to review the pathophysiology, risk factors and treatment of cobalt toxicity. To the best of our knowledge, there are 18 published cases where cobalt metal ion toxicity has been attributed to the use of cobalt-chromium alloys in hip arthroplasty. Of these cases, the great majority reported systemic toxic reactions at serum cobalt levels more than 100 μg/L. This review highlights some of the clinical features of cobalt toxicity, with the goal that early awareness may decrease the risk factors for the development of cobalt toxicity and/or reduce its severity.

Take home message: Severe adverse events can arise from the release of cobalt from metal-on-metal arthroplasties, and as such, orthopaedic surgeons should not only be aware of the presenting problems, but also have the knowledge to treat appropriately.

Cite this article: Bone Joint J 2016;98-B:14–20.

The aim of this review is to address controversies in the management of dislocations of the acromioclavicular joint. Current evidence suggests that operative rather than non-operative treatment of Rockwood grade III dislocations results in better cosmetic and radiological results, similar functional outcomes and longer time off work. Early surgery results in better functional and radiological outcomes with a reduced risk of infection and loss of reduction compared with delayed surgery.

Surgical options include acromioclavicular fixation, coracoclavicular fixation and coracoclavicular ligament reconstruction. Although non-controlled studies report promising results for arthroscopic coracoclavicular fixation, there are no comparative studies with open techniques to draw conclusions about the best surgical approach. Non-rigid coracoclavicular fixation with tendon graft or synthetic materials, or rigid acromioclavicular fixation with a hook plate, is preferable to fixation with coracoclavicular screws owing to significant risks of loosening and breakage.

The evidence, although limited, also suggests that anatomical ligament reconstruction with autograft or certain synthetic grafts may have better outcomes than non-anatomical transfer of the coracoacromial ligament. It has been suggested that this is due to better restoration horizontal and vertical stability of the joint.

Despite the large number of recently published studies, there remains a lack of high-quality evidence, making it difficult to draw firm conclusions regarding these controversial issues.

Cite this article: Bone Joint J 2013;95-B:1595–1602.

Down’s syndrome is associated with a number of musculoskeletal abnormalities, some of which predispose patients to early symptomatic arthritis of the hip. The purpose of the present study was to review the general and hip-specific factors potentially compromising total hip replacement (THR) in patients with Down’s syndrome, as well as to summarise both the surgical techniques that may anticipate the potential adverse impact of these factors and the clinical results reported to date. A search of the literature was performed, and the findings further informed by the authors’ clinical experience, as well as that of the hip replacement in Down Syndrome study group. The general factors identified include a high incidence of ligamentous laxity, as well as associated muscle hypotonia and gait abnormalities. Hip-specific factors include: a high incidence of hip dysplasia, as well as a number of other acetabular, femoral and combined femoroacetabular anatomical variations. Four studies encompassing 42 hips, which reported the clinical outcomes of THR in patients with Down’s syndrome, were identified. All patients were successfully treated with standard acetabular and femoral components. The use of supplementary acetabular screw fixation to enhance component stability was frequently reported. The use of constrained liners to treat intra-operative instability occurred in eight hips. Survival rates of between 81% and 100% at a mean follow-up of 105 months (6 to 292) are encouraging. Overall, while THR in patients with Down’s syndrome does present some unique challenges, the overall clinical results are good, providing these patients with reliable pain relief and good function.

Cite this article: Bone Joint J 2013;95-B, Supple A:41–5.

Symptomatic cobalt toxicity from a failed total hip replacement is a rare but devastating complication. It has been reported following revision of fractured ceramic components, as well as in patients with failed metal-on-metal articulations. Potential clinical findings include fatigue, weakness, hypothyroidism, cardiomyopathy, polycythaemia, visual and hearing impairment, cognitive dysfunction, and neuropathy. We report a case of an otherwise healthy 46-year-old patient, who developed progressively worsening symptoms of cobalt toxicity beginning approximately six months following synovectomy and revision of a fractured ceramic-on-ceramic total hip replacement to a metal-on-polyethylene bearing. The whole blood cobalt levels peaked at 6521 µg/l. The patient died from cobalt-induced cardiomyopathy. Implant retrieval analysis confirmed a loss of 28.3 g mass of the cobalt–chromium femoral head as a result of severe abrasive wear by ceramic particles embedded in the revision polyethylene liner. Autopsy findings were consistent with heavy metal-induced cardiomyopathy.

We recommend using new ceramics at revision to minimise the risk of wear-related cobalt toxicity following breakage of ceramic components.

Cite this article: Bone Joint J 2013;95-B:31–7.

Purpose

Infection following total knee arthroplasty is a devastating complication, requiring considerable effort on the part of the surgeon to eradicate the infection and restore joint function. Two-stage revision is the standard of care in the treatment of peri-prosthetic infection, using a temporary antibiotic-impregnated spacer between procedures. However, controversy remains concerning the use of static versus dynamic spacers, as well as the spacer material. The purpose of this study was to evaluate the clinical outcomes and complications of two-stage revision total knee arthroplasty in patients treated with a metal-on-polyethylene articulating spacer, as compared to those treated with a static antibiotic-impregnated cement spacer at the same centre.

Currently, there are no generally accepted treatments for the prevention of osteonecrosis. To compound this further, despite considerable research efforts, the natural history of this disease remains poorly understood. The disease process appears to be initially asymptomatic, but after symptoms appear, the course becomes rapidly progressive. Clinical studies have shown that, if left untreated, collapse of the femoral head will occur in 80 per cent of the cases or greater within four years. As our knowledge of the etiology and pathogenesis of osteonecrosis improves, new treatments to halt, or at least impede, the progression of the disease may be possible.

Achieving the best outcomes in the treatment of osteonecrosis depends on early, accurate diagnosis, and prompt treatment appropriate for the stage of the disease. In many cases, if treated early, long-term preservation of the native joint is possible. Magnetic resonance imaging allows accurate diagnosis in even the earliest asymptomatic stages of the disease. Non-surgical treatments such as pharmacological agents have shown promise in experimental studies, although further work remains before they are appropriate for widespread use. Various hip salvaging procedures such as core decompression, percutaneous drilling, non-vascularized and vascularized bone grafting, and various osteotomies have been successful in the majority of properly selected patients over follow-up times of a decade or more. Advances in arthroplasty technologies and techniques, including hip resurfacing and modern cementless total hip arthroplasty have allowed patients to return to pain-free, active lifestyles with excellent long-term prosthesis survival.

Current treatments for osteonecrosis, while generally successful, focus on halting or delaying the progression of symptomatic disease. Recent discoveries concerning the relationship between genetic factors and the development of osteonecrosis, as well as the pathophysiologic effects of various indirect and direct risk factors such as corticosteroid use and sickle cell disease, continue to improve our understanding of the underlying disease process. While these discoveries are promising, we must continue to work towards the goal of being able to identify and treat the precursors of osteonecrosis before it progresses to symptomatic disease and threatens the survival of native joints.

Purpose: The literature regarding the outcome of total knee arthroplasty following distal femoral varus osteotomy is limited. The largest published series to date of eleven such patients suggested that medio-lateral constrained implants are commonly required as ligament balancing is difficult. This study presents mid-term outcomes of patients treated with total knee arthroplasty following distal femoral varus osteotomy at a single center.

Method: Twenty-two consecutive distal femoral varus osteotomies (21 patients) converted to total knee arthroplasties were reviewed at a mean follow-up of five years (range, two to 14 years). The mean duration between osteotomy and conversion to arthroplasty was 12 years (range, three to 21 years). In 14 patients (15 knees) the underlying etiology for the femoral osteotomy was primary knee osteoarthritis with valgus deformity, while in seven patients the procedure was performed to unload a fresh osteochondral allograft of either the lateral tibia (five patients) or femur (two patients). It is the authors’ routine to use posterior stabilized implants were used in all total knee arthroplasty surgeries. Femoral stems were used in six knees in which the bone quality was clinically determined by the surgeon to be sufficiently deficient to predispose to periprosthetic fractures, while the remaining sixteen knees were treated with unstemmed components. Modified knee society scores were used to evaluate the clinical outcomes preoperatively and at most recent follow-up.

Results: The mean knee society knee and function scores in surviving knees improved from 50 points (range, 10 to 75 points) and 50 points (range, 30 to 70 points) pre-operatively, to 91 points (range, 67 to 100 points) and 64 points (range, 50 to 70 points) at final follow-up, respectively. The mean arc of motion improved from 94 degrees (range, 70 to 115 degrees) to 114 degrees (range, 90 to 130 degrees). Two patients underwent revision arthroplasty for polyethylene wear and component loosening at eight and 11 years following the index arthroplasty, respectively. There were no fractures, infections or wound complications.

Conclusion: Total knee arthroplasty following distal femoral varus osteotomy reliably decreases pain and improves knee function. Standard posterior stabilized components provide satisfactory stability after appropriate ligamentous balancing, without the need for stemmed or highly constrained components in the majority of patients.

Purpose: Spontaneous osteonecrosis of the knee is a potentially greatly debilitating condition. While success has been reported with non-operative treatment of this disorder in its earliest stages, knee arthroplasty is the only viable modality if allowed to progress to condylar collapse. The purpose of this report is to review the etiologic and pathophysiologic principles of spontaneous osteonecrosis of the knee, to present our experience with joint-preserving surgical treatment of this condition, and finally to introduce a treatment algorithm developed based on this knowledge.

Method: Seventeen patients with a clinical and/or radiographic a diagnosis of spontaneous osteonecrosis of the knee, and exclusion of secondary osteonecrosis, who failed non-operative modalities were treated with joint-preserving surgery at a single center between January 2000 and December 2006. Treatment modalities included arthroscopy, and either percutaneous core decompression and/or osteochondral autograft transfer. Three knees were lost to follow-up, leaving 14 knees with a mean follow-up of 37 months (range, 11 to 84 months).

Results: Twelve of 14 knees (86%) had knee joint survival with a mean Knee Society Score of 80 points (range, 45 to 100 points) at final follow-up. One patient was treated with serial core decompression followed by osteochondral transfer, and was included in both groups. Six of 7 patients (86%) treated with core decompression alone had a successful clinical outcome, as did 7 of 8 patients (87%) treated with osteochondral autograft transfers. Two patients (14%) progressed to condylar collapse, and were treated with total knee arthroplasty with successful results.

Conclusion: Based on these results, we propose a treatment algorithm that begins with non-operative treatment, followed by joint-preserving surgery consisting of arthroscopy, core decompression, and/or osteochondral autograft transfer. Although our sample size is small, the results suggest that this proposed treatment algorithm can successfully postpone the need for knee arthroplasty in selected patients with pre-collapse spontaneous osteonecrosis of the knee.

Purpose: Many strategies have been reported for decreasing the cost of orthopaedic procedures, including negotiating lower prices with manufacturers and using lower-cost generic implants, but prosthetic waste has not been investigated. The purpose of this study was to characterize the present and potential future cost of intra-operative waste of hip and knee implants.

Method: A regional prospective assessment of implant waste was performed from January 2007 to June 2008, evaluating the incidence and reasons for component waste, the cost of the wasted implants, and where the cost was absorbed (hospital or manufacturer). Using published data on nationwide arthroplasty volumes, the results were extrapolated to the whole of the United States. Finally, based on peer-reviewed estimates of nationwide arthroplasty volumes for the next 20 years, a projection was made about the future cost burden of implant waste.

Results: Implant waste occurred in 79 of 3443 recorded procedures (2%), with the surgeon bearing primary responsibility in 73% of occurrences. The annualized waste cost was $109,295.35, with 67% absorbed by the hospital. When extrapolated to the whole of the United States, the annual cost to hospitals of hip and knee prosthetic waste is $36,019,000, and is estimated to rise to $112,033,000 in current dollars by the year 2030.

Conclusion: This study discovered a notable incidence of intra-operative hip and knee implant waste, with the majority of cases attributed to the surgeon, and representing an important additional cost burden on hospitals. With arthroplasty rates projected to increase markedly over the next twenty years, this waste represents a potentially noteworthy target for educational programs and other cost containment measures in orthopaedic surgery.

Purpose: Minimally-invasive total knee arthroplasty has generated tremendous recent interest, but there have been reports of complications resulting from these new techniques. However, most studies have less than one year follow-up and are anecdotal in their results. The purpose of this study was to retrospectively evaluate a series of 1,000 consecutive minimally invasive total knee arthroplasties, to describe the clinical and radiographic complications of this technique, to determine whether complication rates changed with experience, and finally to compare complication rates to a match group operated by the same surgeon.

Method: Clinical and radiographic data were reviewed for the first 1,000 consecutive minimally-invasive knees (820 patients) performed by a single surgeon with a minimum 2 year post-operative period. All patients were operated using the mid-vastus approach, with a mean incision length of 10 cm (range, 8 to 13 cm). Nine patients were lost prior to 2 year follow-up, leaving 990 knees (811 patients) in this report with annual follow-up. After determining overall results, data was stratified into 100-knee groups to determine whether complication rates changed over time. Finally, complication rates were compared to a matched group of 50 knees operated by the same surgeon.

Results: There were a total of 45 clinical complications (4.5%), including 20 (2.0%) manipulations under anesthesia, 12 (1.2%) arthroscopies for painful crepitus, 4 (0.4%) component changes, and 3 (0.3%) spacer changes. There were 3 (0.3%) impending radiographic failures. Stratification of results showed a complication rate of 6% over the first 200 knees, and 1% over the subsequent 800 knees. In comparison, the matched group had a complication rate of 4% over mean follow-up of 3 years (range, 2 to 4).

Conclusion: This large series with minimum two year follow-up describes many of the long-term complications of this technique. Additionally, this large series suggests that high volume knee surgeons may require as many as 200 minimally invasive arthroplasties before achieving optimum proficiency with this technique. Nonetheless, comparison to a matched group suggests that even with this learning curve, complication rates need not increase markedly during this period if surgeons remain attentive to the potential complications associated with minimally invasive techniques.