Knee arthroplasty for spontaneous osteonecrosis of the knee: unicompartimental vs bicompartimental knee arthroplasty

Bone marrow edema of the knee: a narrative review

Bone marrow edema (BME) is a frequent MRI finding in patients with knee pain. According to the etiology, BME of the knee can be classified into three main categories: ischemic, mechanic, and reactive. The diagnosis may be difficult, because of the specificity of symptoms and the poor radiographic findings. MRI is the gold standard, showing an area of altered signal of the bone with an high signal intensity on fat-suppressed, T2 weighted images, usually in combination with an intermediate or low signal intensity on T1 weighted images. Bone marrow edema tends to be self-limiting and, in most cases, resolves without any consequences in a varying amount of time. However, since it may evolve to complete joint destruction, early diagnosis and correct treatment are crucial to prevent the articular degeneration. Conservative therapy is the first step, with no weight-bearing for 3 to 6 weeks on the affected side, in combination with the administration of anti-inflammatory drugs or painkillers to manage symptoms. In non-responding forms and more advanced stages, minimally invasive preservative surgery can provide significant results, with subchondroplasty and core decompression being the two main procedures available. Knee arthroplasty, both total (TKA) or unicompartmental (UKA), is the only effective option when the degradation of cartilage is diffuse and in patients with subchondral bone collapse.

Functional improvement of unicompartmental knee arthroplasty compared with total knee arthroplasty for subchondral insufficiency fracture of the knee

Subchondral insufficiency fracture of the knee (SIFK) causes acute knee pain in adults and often requires surgical management. Unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) are the two most common surgical treatments for SIFK. While both UKA and TKA have their advantages, there is no consensus for SIFK localized on the medial compartment. We hypothesized that patients with SIFK treated with UKA would show superior patient-reported outcomes compared to those who underwent TKA. A total of 90 patients with SIFK located medially were included in the TKA (n = 45) and UKA (n = 45) groups. Size of SIFK lesions were measured on MR images. Patient reported outcomes in the form of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Hospital Special Surgery (HSS) scores, and Knee Society Scores (KSS) were assessed preoperatively, postoperative 6, 12 months, and at the final follow-up. There were no differences in the size of the SIFK lesion between two groups. At 6 months, WOMAC score was better in the UKA group than the TKA group (p < .01). Both groups had a significant improvement in WOMAC, HSS, and KSS scores at the final follow-up compared to preoperative scores. The UKA group had better range of motion of the knee preoperatively and postoperatively than the TKA group (p < .01 and p < .01). UKA group showed a higher relative risk than the TKA group in terms of complications (RR = 3.0) but with no statistical significance (P = 0.31). Unicompartmental arthroplasty and total joint arthroplasty can produce successful outcomes in patients with SIFK with proper patient selection, regardless of the size of SIFK lesion.

Subchondral Insufficiency Fractures of the Knee: A Clinical Narrative Review

» Subchondral insufficiency fractures of the knee (SIFKs) are subchondral plate fractures with a prevalence of 2% to 4% of all knee injuries.» Magnetic resonance imaging is the gold standard for evaluating SIFK, while plain radiographs have limited the use in the diagnosis of SIFK.» Among patients with SIFK, 50% to 100% have meniscal pathology.» Medical therapies and standard treatments traditionally used in the management of knee osteoarthritis differ from recommended management of SIFK patients.» Randomized controlled trials and cohort studies with long-term follow-up are needed to determine the optimal rehabilitation protocol, interventional therapy, and prognosis of SIFK patients.

Unicompartmental knee arthroplasty (UKA) for primary spontaneous osteonecrosis of the knee (SONK): a systematic review

Introduction

The role of unicompartmental knee arthroplasty (UKA) in spontaneous osteonecrosis of the knee (SONK) is still controversial.

Materials and methods

We performed a systematic review to evaluate all available current literature on UKA in the setting of SONK. A comprehensive electronic research was performed using the PubMed, Embase, Web of Science, and Cochrane databases with keywords related to SONK and knee arthroplasty. Studies were selected with predetermined inclusion criteria: 1) studies that specifically assessed SONK treated with UKA; 2) studies reporting implant survival rate and global clinical outcomes; 3) studies with a minimum follow up of 1 year. We excluded articles not written in English, articles that did not differentiate between primary and secondary osteonecrosis and articles published before 2000.

Results

The overall research process produced 19 studies. We extrapolated data of a total of 717 unicompartimental knee arthroplasty procedures (1,39% lateral UKA, 98,61% medial UKA). Extracted data include years of follow-up, patient demographics, laterality of lesion, radiological findings, unicompartimental knee arthroplasty implants, reason of revision, revision rate, maximum knee flexion, knee clinical outcomes score, and Kaplan-Meier survival curves. The data collected show that UKA had acceptable survival rates as well as revision rates and good clinical outcomes both in the short- and long-term.

Conclusion

UKA is an optimal treatment choice for primary SONK when correctly indicated in a carefully selected subset of patients, with no significant difference compared to osteoarthritis. Attention must be paid to distinguish the primary from secondary SONK, as the latter could lead to worse outcomes.

Satisfactory Outcomes of All-Poly Fixed Bearing Unicompartmental Knee Arthroplasty for Avascular Osteonecrosis Versus Osteoarthritis: A Comparative Study With 10 to 22 Years of Follow-up

BACKGROUND

While good mid-term results for treating spontaneous knee osteonecrosis (SPONK) with unicompartmental knee arthroplasty (UKA) have been reported, concerns remain about implant survival at long-term. This study aimed to compare outcomes and survivorship of UKA for SPONK vs osteoarthritis at a minimum of 10 years.

METHODS

This case-control study included medial UKA for femoral SPONK operated between 1996 and 2010 with a minimum 10-year follow-up (n = 47). Each case was matched with a medial UKA for osteoarthritis based on body mass index (BMI), gender, and age. Knee Society Score (KSS), complications and radiological (loosening) data were collected at the last follow-up. Kaplan-Meier survivorship analysis was performed using revision implant removal as endpoint.

RESULTS

The mean follow-up was 13.2 years (range 10 to 21 years). Mean age and BMI were 72.9 ± 8.4 years and 25.5 ± 3.6 Kg/m² in SPONK group. At last follow-up, knee and function KSS were 89.5 ± 12 and 79 ± 18 in SPONK group vs 90 ± 15 (P = .85) and 81.7 ± 17 (P = .47) in control group. Complications and radiological results showed no significant differences. The survival rate free from any revision was 85.1% at last follow-up in SPONK group and 93.6% in control group (P = .23). The leading cause for revision was aseptic tibial loosening (57.1%) in SPONK group. The 15-year survival estimate was 83% in SPONK group.

CONCLUSION

Satisfactory clinical outcomes at long-term after UKA for femoral SPONK were observed, similar to those after UKA for osteoarthritis, despite a higher risk of tibial loosening in the SPONK group. No symptomatic femoral loosening leading to a revision was observed.

LEVEL OF EVIDENCE

IV.

The primary stability of the femoral component in cemented single and twin peg Oxford unicompartmental knee arthroplasty under adverse conditions

Aims

The cemented Oxford unicompartmental knee arthroplasty (OUKA) features two variants: single and twin peg OUKA. The purpose of this study was to assess the stability of both variants in a worst-case scenario of bone defects and suboptimal cementation.

Methods

Single and twin pegs were implanted randomly allocated in 12 pairs of human fresh-frozen femora. We generated 5° bone defects at the posterior condyle. Relative movement was simulated using a servohydraulic pulser, and analyzed at 70°/115° knee flexion. Relative movement was surveyed at seven points of measurement on implant and bone, using an optic system.

Results

At the main fixation zone, the twin peg shows less relative movement at 70°/115°. At the transition zone, relative movements are smaller for the single peg for both angles. The single peg shows higher compression at 70° flexion, whereas the twin peg design shows higher compression at 115°. X-displacement is significantly higher for the single peg at 115°.

Conclusion

Bony defects should be avoided in OUKA. The twin peg shows high resilience against push-out force and should be preferred over the single peg.

Cite this article: Bone Joint Res 2022;11(2):82–90.

Total and unicondylar knee arthroplasty are equivalent treatment options in end-stage spontaneous osteonecrosis of the knee, and the size of the lesion has no influence on the results

PURPOSE

The purpose of the present study was to compare total (TKA) and unicondylar (UKA) knee arthroplasty for spontaneous osteonecrosis of the knee (SONK), and to investigate potential correlations to radiographic parameters.

METHODS

All consecutive patients with a magnetic resonance imaging (MRI) proven SONK treated with either TKA or UKA between 2002 and 2018 were analysed. The primary outcomes were postoperative complications and failure rates. Functional assessment included Knee Society Score (KSS), WOMAC Score, and range of motion. A novel three-dimensional measurement method was established to determine the size of the osteonecrotic lesion. All outcome parameters were correlated to the size of the necrotic lesion using Spearman's rank correlation.

RESULTS

The two treatment groups (34 TKAs, 37 UKAs) did not differ regarding age, body mass index, and ratio of the volume of the necrotic lesion to the volume of the femoral condyle (n.s.). At a mean follow-up of 6.6 years, patients with UKA had better functional outcomes compared to patients with a TKA (WOMAC Score 1.0 vs. 1.6, p = 0.04; KSS pain 86 vs. 83, n.s), with a similar complication rate. No correlation was found between necrotic lesion size and failure rate (n.s.).

CONCLUSION

UKA is a valuable treatment option for SONK leading to good functional results and a low failure rate. In case of a surgeon's concern regarding implant anchorage, TKA represents an equivalent solution. The MR-tomographic size of the osteonecrotic lesions seems to have no influence on the results.

LEVEL OF EVIDENCE

III.

Postoperative clinical outcomes of unicompartmental knee arthroplasty in patients with isolated medial compartmental osteoarthritis following medial meniscus posterior root tear

Background

Cartilage degradation progresses rapidly following medial meniscus posterior root tear (MMPRT). Unicompartmental knee arthroplasty (UKA) has been performed for medial compartmental osteoarthritis following MMPRT. We evaluated the clinical and radiographic outcomes of UKA for medial compartmental osteoarthritis after an untreated MMPRT.

Methods

Twenty-one patients who underwent UKA for isolated medial compartment osteoarthritis following MMPRT were retrospectively investigated. Clinical outcomes were assessed using the Knee Injury and Osteoarthritis Outcome Score and knee range of motion. The posterior tibial slope and tibial component inclination were evaluated using plain radiographs.

Results

The mean follow-up periods were 25.5 ± 13.8 months. Clinical outcomes improved significantly postoperatively. The mean postoperative knee extension angle was −1.1° ± 2.1°, and the knee flexion angle was 134.3° ± 4.9°. The posterior tibial slope angle decreased from 9.0° ± 2.0° preoperatively to 5.4° ± 1.8° postoperatively, and postoperative tibial component inclination at the final follow-up was 2.9° ± 1.1° varus. No aseptic loosening or deep infections were observed.

Conclusion

UKA significantly improved clinical outcomes and could be a viable surgical option for treating isolated medial compartmental osteoarthritis accompanied by untreated MMPRT.

A Retrospective Study of Unicompartmental Knee Arthroplasty Functional Outcome and the Incidence of Medial Meniscus Posterior Root Tear in Spontaneous Osteonecrosis of the Knee

Background

Spontaneous osteonecrosis of the knee (SONK) can lead to severe knee osteoarthritis predominantly localized to the medial compartment. We aimed to determine whether unicompartmental knee arthroplasty was an effective treatment for primary SONK.

Methods

We analyzed the functional outcomes in 23 patients with SONK (with a magnetic resonance imaging- (MRI-) confirmed diagnosis) who underwent UKA at a single center. The mean follow-up time was 67 months post-UKA.

Results

Significant improvements in function were indicated by reduced Oxford Knee and Visual Analogue Scale scores after UKA, and there were no specific complications after the procedures. The incidence of MRI-identified medial meniscus posterior root tear (MMPRT) was 69.6% (16/23).

Conclusion

Unicompartmental arthroplasty for SONK is less destructive to the native knee structure than total knee arthroplasty but can achieve comparable prognosis with strict patient selection. While the precise etiology of SONK is unknown, one theory posits that a MMPRT may change the biomechanical circumstances of the knee joint, leading to osteonecrosis. Although not confirmatory, the high prevalence rate suggests that MMPRT may have a key role in the development of SONK. UKA is an effective treatment option for SONK, resulting in significant functional improvement. Long-term (>10 years) outcomes should be investigated.

Alternate treatment approach to subchondral insufficiency fracture of the knee utilizing genicular nerve cooled radiofrequency ablation and adjunctive bisphosphonate supplementation: A case report

Subchondral insufficiency fractures of the knee are commonly misdiagnosed fractures that are both very painful and difficult to treat. A conservative treatment modality to control symptoms during rehabilitation has not previously been described. This case report presents the alternate use of cooled radiofrequency ablation technique of the genicular nerves for pain relief and bisphosphonate infusion to address the underlying poor bone mineralization/density with imaging follow-up before and after instituted treatments. A middle-aged female patient presenting with atraumatic pain in the medial aspect of the left knee diagnosed on an original magnetic resonance imaging as an insufficiency fracture and debilitating pain. Multiple-surgeon opinions of total knee arthroplasty were not a consideration the patient wanted or could consider given her lifestyle. Cooled radiofrequency ablation of the genicular nerve branches was performed with significant-complete pain relief achieved that lasted at least 6 months. Bisphosphonate infusions were instituted to address the underlying osteoporosis detected by a dual energy X-ray absorptiometry (DEXA) scan. Clinical performance after the radiofrequency ablations was followed with clinically validated surveys (The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)/Knee Injury and Osteoarthritis Outcome Score (KOOS)) at 2 weeks, 1, 3, and 6 months. Patient was also asked to follow a restricted-modified weight-bearing plan for 3 months followed by physical therapy. Eight weeks apart of bisphosphonate infusions were delivered after proper administration of vitamin D. There was resolution of the insufficiency fracture at the medial femoral condyle between the magnetic resonance imaging exams within 4.5 months apart treated with restricted weight-bearing regimen. Pain resolution, significant improved function, and range of motion were the end results of our instituted treatment plan. This case reports presents an alternate pathway for the treatment of this condition especially when there is lack of consensus among physicians in how to best address this condition.

Spontaneous osteonecrosis of the knee: what do we know so far? A literature review

PURPOSE

Spontaneous osteonecrosis of the knee (SONK) is said to be a relatively common disease which may lead to an end-stage osteoarthritis of the knee. The aim of this paper was to review the literature on this field published until now, discuss the results of both conservative and surgical treatment options, as well as to introduce new methods of treatment, which may be applicable in SONK treatment.

METHODS

We searched the PubMed and Cochrane databases until November 2019 and presented the most recent findings in this work.

RESULTS

The exact aetiology of SONK still remains unclear; however, recent studies suggested that early stage of SONK is rather a result of the subchondral fracture than primary osteonecrosis. So far described conservative treatment includes non-weight bearing or protected weight bearing with a knee brace, nonsteroidal anti-inflammatory drugs, analgesics, and bisphosphonates. Surgical management includes arthroscopic debridement, core decompression, osteochondral autograft, high tibial osteotomy, and unicompartmental knee arthroplasty or total knee arthroplasty.

CONCLUSIONS

Although the aetiology of SONK remains unknown, there are many treatment options, and the choice of the most suitable one is challenging. We think that subchondroplasty may be one of the effective methods.

Surgical Technique and Clinical Outcomes of Osteochondral Autograft Transplantation for Large Osteonecrotic Lesions of the Femoral Condyle With Residual Normal Cartilage: The Eyeglass Technique

Background:

Osteochondral autograft transplantation (OAT) is usually performed for a defect that is <400 mm² because of the limitations of autografts.

Purpose:

To present the surgical technique and clinical outcomes of OAT using the eyeglass technique for large osteonecrotic lesions of the femoral condyle (LOFs) (>400 mm²) with residual normal cartilage.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Cases (group 1) included 15 patients (18 knees) who underwent OAT using the eyeglass technique for LOFs with residual normal cartilage, while controls (group 2) included 11 patients (11 knees) who underwent OAT using the standard technique for small osteonecrotic lesions of the femoral condyle (≤400 mm²). Clinical outcomes were evaluated preoperatively and at the final follow-up (group 1, 56 months; group 2, 48 months) according to the International Knee Documentation Committee (IKDC) objective grade, the IKDC subjective score, and the Japanese Orthopaedic Association (JOA) score.

Results:

The mean lesion size was 685 mm² in group 1 and 230 mm² in group 2. Patients in group 1 had postoperative scores equivalent to those in group 2. The postoperative IKDC subjective scores in group 1 (mean, 86.9) and group 2 (mean, 87.0) showed no significant difference at the final follow-up (P = .653). For postoperative IKDC objective grades, 83.3% of group 1 and 81.8% of group 2 were graded as “nearly normal” or better, and no significant intergroup difference was found for the IKDC objective grade (P = .989). Also, no significant intergroup difference was found for the postoperative JOA score (group 1, 93.9; group 2, 81.4; P = .480). Nine second-look arthroscopic procedures were performed in group 1 compared with 4 in group 2, and all patients had plugs that were graded as “nearly normal” or better by the International Cartilage Repair Society classification system.

Conclusion:

The postoperative results of patients who underwent OAT using the eyeglass technique for large osteonecrotic lesions (>400 mm²) were equivalent to the results of patients who underwent OAT using the standard technique for small osteonecrotic lesions (≤400 mm²).

Unicompartmental knee arthroplasty for spontaneous osteonecrosis of the knee: A meta-analysis

BACKGROUND

Spontaneous osteonecrosis of the knee (SONK) is a poorly understood but debilitating disease entity. Total knee arthroplasty (TKA) is the standard of care for those patients who fail conservative management, but considering SONK's predilection for affecting a single knee compartment, unicompartmental knee arthroplasty (UKA) appears to be a more tailored option. Unfortunately, conflicting data exist on the utility of UKA in SONK. Thus, the purpose of this study was to evaluate functional outcomes and revision rates of UKA in the setting of SONK.

METHODS

A systematic literature search was performed to evaluate all studies examining patients who underwent UKA for SONK. Screening of the articles was performed using multiple Boolean search strings, methodological index for non-randomized studies criteria, and other selected exclusion criteria.

RESULTS

Seven studies were included, with a total of 276 knees (273 patients). The mean age was 68 years (64-74 years), with a mean body mass index of 26 kg/m² (25-29 kg/m²). The final range of motion was 125° (124-126°). Standardized mean difference (SMD) of clinical improvement pre- and post-outcome was 3.39 ( p < 0.001). The improvement in the visual analog score was 57.03 points, with an SMD of 4.57 ( p < 0.001). Revision rates were determined to be 5.51% (95% confidence interval of 1.96-10.69%).

CONCLUSION

Our meta-analysis demonstrated that in properly selected patients, UKA could be an excellent alternative to TKA for patients with SONK. These data show that UKA has few complications, significant improvements on functional outcomes, and good survivorship at a mean follow-up of 6 years.

Medial Unicompartmental Knee Arthroplasty for the Treatment of Focal Femoral Osteonecrosis

BACKGROUND

Previous research has indicated that unicompartmental arthroplasty may be an effective treatment for focal osteonecrosis in the knee; however, these reports have been composed of small patient cohorts and without characterization of the osteonecrotic lesions. Therefore, the purpose of this study was to investigate the effectiveness of unicompartmental arthroplasty for the treatment of focal osteonecrosis within the medial femoral condyle including an assessment of lesion size.

METHODS

A consecutive series of >5,000 unicompartmental knee arthroplasties performed at a single institution was retrospectively reviewed to identify cases of medial femoral condyle osteonecrosis with a minimum 2-year follow-up. Lesion size was classified according to the ratio of lesion width to condylar width, as well as lesion depth relative to condylar depth. Patient-reported outcome measures and need for a revision procedure were studied.

RESULTS

Sixty-four patients (32 males, 32 females; 65 knees) with a mean age of 64 years were included. The mean patient follow-up was 5.3 years (range, 2 to 12 years). The mean ratio of lesion width to condylar width was 64%, the mean lesion depth was 1.11 cm, and 82% of cases demonstrated subchondral collapse. At the time of the latest follow-up, patients demonstrated substantial improvements in the pain, function, and clinical components of the Knee Society Score, by 36, 25, and 51, respectively. Four patients (6%) required a revision, of which only 1 was for aseptic loosening of the femoral component.

CONCLUSIONS

Unicompartmental arthroplasty is an effective treatment for advanced-stage focal osteonecrosis of the medial femoral condyle. Loss of component fixation to the femoral condyle did not appear to be a substantial concern because there was only 1 femoral failure as a result of aseptic loosening, despite lesions affecting a significant portion of the femoral condyle.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Does unicompartmental knee arthroplasty have worse outcomes in spontaneous osteonecrosis of the knee than in medial compartment osteoarthritis? A systematic review and meta-analysis

INTRODUCTION

The role of unicompartmental knee arthroplasty (UKA) in spontaneous osteonecrosis of the knee (SONK) remains controversial, even though SONK involves only one compartment of the knee joint. We aimed to compare the survival rate and clinical outcomes of UKA in SONK and medial compartment osteoarthritis (MOA) via a meta-analysis of previous studies.

MATERIALS AND METHODS

MEDLINE, Embase, and Cochrane Library were searched up to January 2018 with keywords related to SONK and knee arthroplasty. Studies were selected with predetermined inclusion criteria: (1) medial UKA as the primary procedure, (2) reporting implant survival or clinical outcomes of osteonecrosis and osteoarthritis, and (3) follow-up period > 1 year. Quality assessment was performed using the risk of bias assessment tool for non-randomized studies. A random-effects model was used to estimate the pooled relative risk (RR) and standardized mean difference.

RESULTS

The incidence of UKA revision for any reason was significantly higher in SONK than in MOA group (pooled RR = 1.83, p = 0.009). However, the risk of revision due to aseptic loosening was not significantly different between the groups. Moreover, when stratified by the study quality, high-quality studies showed similar risk of overall revision in SONK and MOA (p = 0.71). Subgroup analysis revealed no significant difference in failure between SONK and MOA after cemented mobile and fixed bearing UKA. Results of uncemented UKA were reported only in one study, which showed higher failure of SONK compared to MOA. Clinical outcomes after UKA were similar between SONK and MOA (p = 0.66).

CONCLUSIONS

Cemented UKA has similar survival and clinical outcomes in SONK and MOA. Prospective studies designed specifically to compare the UKA outcomes in SONK and MOA are necessary.

Long-Term Results of Medial Unicompartmental Knee Arthroplasty for Knee Avascular Necrosis

BACKGROUND

Numerous series have documented short and mid-term successes with cemented, metal-backed modern unicompartmental knee arthroplasty (UKA) for avascular osteonecrosis of the knee (AVN). However, data are lacking regarding long-term implant fixation and patient function. The aim of this study is therefore to evaluate the long-term clinical outcome and implant survivorship of patients who underwent UKA for medial knee osteonecrosis (ON).

METHODS

Twenty-nine consecutive UKAs performed by 2 senior surgeons (>50 UKAs a year) in 28 patients (19 women and 9 men with a mean age of 67 years) with medial unicompartmental AVN of the knee between 1989 and 2001 were retrospectively reviewed. AVN was diagnosed using X-ray, magnetic resonance imaging scan, and finally confirmed by postoperative sample analysis. The mean patient body mass index was 27 kg/m². Etiologies were spontaneous/idiopathic AVN in 19 knees (66%) and secondary AVN in 10 knees (33%). The mean follow-up was 21 years (range 15-26).

RESULTS

At 15 years, survivorship of the components free of revision for any cause was 92% (95% confidence interval 87-97). At latest follow-up, 26 years, survivorship of the components free of revision for any reason was 83% (95% confidence interval 74-95). No survivorship difference was found between the patients suffering from spontaneous or secondary ON of the knee (83% vs 90%, P = .6). At latest follow-up, the mean Knee Society Scoring system Knee was 89 points (range 68-100) and 83 (range 66-96) for Knee Society Scoring system Function.

CONCLUSION

In the longest series to date, medial UKA for treatment of AVN was associated with high survival rates and stable clinical improvement. UKA is a durable and efficient option to treat patients with unicompartmental ON of the knee.

LEVEL OF EVIDENCE

IV.

Osteonecrosis

Younger patients are affected more often by osteonecrosis than by osteoarthritis, and osteonecrosis has significantly greater long-term morbidity.

Corticosteroids are the most common cause of nontraumatic osteonecrosis.

The femoral head is the most common site of osteonecrosis.

In rare instances, osteonecrosis of the jaw has been associated with bisphosphonate exposure. This phenomenon is more common with repeated intravenous infusions of bisphosphonates.

Case reports of osteonecrosis of the jaw in association with other medications, such as denosumab, have been reported.

The final common pathway in the pathogenesis of osteonecrosis is disruption of blood supply to a segment of bone.

Abnormalities in lipid metabolism, bone homeostasis, regulation of apoptosis, coagulopathies, innate immunity, and oxidative stress may play a role in the pathogenesis of osteonecrosis.

Epigenetics may alter the predisposition to develop osteonecrosis.

MRI is currently the optimal test for early diagnosis and identification of the extent of osteonecrosis.

Nonsurgical treatment of osteonecrosis does not change the natural history of the disease.

Although surgical treatment of femoral head osteonecrosis has many variations, most symptomatic patients eventually require total hip arthroplasty.

Knowledge of risk factors and early detection are crucial to the successful management of osteonecrosis.

Because of the lack of successful treatment options, new modes of management focus on the prevention of osteonecrosis.

High tibial osteotomy combined with cancellous bone graft and osteochondral autograft transplantation in a patient with massive osteochondral defects in the medial femoral condyle

Treatment of massive osteochondral defects of the medial femoral condyle is challenging. A 46-year-old man who had a medial femoral condyle fracture on his left knee underwent osteosynthesis in a hospital, but the pain remained and the patient was referred to our hospital 8 months after the surgery. Radiographs showed a varus alignment of the leg, and magnetic resonance image showed a massive necrotic area in the medial femoral condyle. The patient received high tibial osteotomy (HTO) combined with iliac cancellous bone graft and an osteochondral autograft transplantation. Pain and the knee function markedly improved 2 years after the surgery. A second look arthroscopy showed a well-covered bone graft site with cartilaginous tissue and a well-integrated osteochondral plug. HTO combined with cancellous bone autograft and osteochondral autograft transplantation could be an effective treatment for patients presenting with a varus knee deformity associated with massive osteochondral defects in the medial femoral condyle.

Unicompartmental knee arthroplasty for spontaneous osteonecrosis

BACKGROUND

Unicompartmental knee arthroplasty (UKA) is an effective treatment option for medial compartment osteoarthritis (OA) of the knee. Whether spontaneous osteonecrosis of the knee (SPONK) can be successfully treated with UKA remains controversial. This study evaluated the clinical and radiological results of patients with SPONK who were treated by UKA using Oxford phase III prostheses.

METHODS

We compared a prospective series of 23 UKA cases operated for SPONK with 235 UKA cases operated for OA. All patients underwent Magnetic Resonance Imaging (MRI) to confirm the diagnosis and exclude any major lesion in the lateral compartment. The stage, condylar ratio, and volume of the necrotic lesion were evaluated. The pre and postoperative Oxford knee scores (OKSs) were compared.

RESULTS

The mean follow-up was 60 months. No statistical differences in complication rates between the groups were found. The mean OKS improved from 39.48 ± 5.69 to 18.83 ± 3.82 ( p < 0.05). There were no significant differences in the pre and postoperative OKS between the different groups.

CONCLUSION

SPONK can be successfully treated with UKA, with a favorable short- to mid-term follow-up.

Can a biomimetic osteochondral scaffold be a reliable alternative to prosthetic surgery in treating late-stage SPONK?

BACKGROUND

This study aimed to assess the reliability of the Maioregen® biomimetic osteochondral scaffold (Finceramica Faenza SpA, Faenza, Italy) as a salvage and joint-preserving procedure in the treatment of late-stage osteonecrosis of the knee.

METHODS

Eleven active patients aged under 65years and presenting with clinical and radiological signs of SPONK were treated with Maioregen®. All were clinically evaluated pre-operatively and yearly thereafter for a minimum of two years. Subjective IKDC and Lysholm Knee Scale scores were used to assess clinical outcome. A VAS scale served to quantify pre-operative pain and post-operative pain. Activity levels were evaluated pre-operatively and at follow-up using the Tegner Activity Scale.

RESULTS

Subjective IKDC (40±15.0 to 65.7±14.8 (mean±SD)) and Lysholm Knee Scale (49.7±17.9 to 86.6±12.7 (mean±SD)) scores improved significantly from pre-operative evaluation (p<.01). VAS scores decreased from a pre-operative mean (±SD) of 6.3±2.5 to 1.6±2.7 at two years. The Tegner Activity Scale showed no significant differences between pre-injury and two-year follow-up. Two out of the 11 patients were symptomatic at 18months post implant and progressed to condylar collapse. These patients required total knee arthroplasty.

CONCLUSIONS

Use of a biomimetic scaffold can be a valid option in the surgical treatment of SPONK in relatively young active patients. Indeed, this surgical technique, originally developed for osteochondritis dissecans, has been found to give good clinical results at medium-term follow-up of late-stage osteonecrosis treatment and could postpone or even avoid the need for joint replacement procedures.

[Femoral osteonecrosis - Ahlbaeck's disease]

Osteonecrosis of the knee can present as a spontaneous, primary (SPON) or a secondary clinical entity (SON). The natural history of SPON follows a course of several sequential stages which seem to be irreversible in later stages of both entities. Early diagnosis of ON is crucial and the earlier the stage of the lesion at the time of diagnosis, the better the prognosis. Clinically, early diagnosis and treatment of ON might prevent unnecessary surgery in cases with a concomitant degenerative meniscal tear. From a medicolegal viewpoint early-stage ON should be ruled out prior to surgery as arthroscopy has recently been associated with ON. Recent biopsy studies showed that SPONK is most likely caused by insufficiency fractures which seem to appear as osteonecrotic lesions in later stages of the disease due to failed bone healing.

Osteonecrosis

Osteonecrosis affects younger patients more often than osteoarthritis and has significantly greater long-term morbidity.

Corticosteroids constitute the most common cause of nontraumatic osteonecrosis.

The femoral head is the most common site of osteonecrosis.

Bisphosphonate use is associated with osteonecrosis of the jaw.

The final common pathway in the pathogenesis of osteonecrosis is disruption of blood supply to a segment of bone.

Abnormalities in lipid metabolism, bone homeostasis, regulation of apoptosis, coagulopathies, and oxidative stress may play a role in the pathogenesis of osteonecrosis.

Magnetic resonance imaging is currently the optimal test for early diagnosis and identification of the extent of osteonecrosis.

Nonsurgical treatment of osteonecrosis does not change the natural history of the disease.

Although there are many variations on surgical treatment of femoral head osteonecrosis, most patients eventually require total hip arthroplasty.

Knowledge of risk factors and early detection are crucial to the successful management of osteonecrosis.

Due to the lack of successful treatment options, new modes focus on prevention of osteonecrosis.

Is unicompartmental arthroplasty an acceptable option for spontaneous osteonecrosis of the knee?

BACKGROUND

The literature suggests survivorship of unicompartmental knee arthroplasties (UKAs) for spontaneous osteonecrosis of the knee ranges from 93% to 97% at 10 to 12 years. However, these data arise from small series (23 to 33 patients), jeopardizing meaningful conclusions.

QUESTIONS/PURPOSES

We determined (1) the longer-term survivorship of UKAs in a larger group of patients with spontaneous osteonecrosis of the knee; (2) their subjective, symptomatic, and functional outcomes; and (3) the percentage of failures and reasons for failures to identify relevant indications, contraindications, and technical parameters for treatment with a modern implant design.

METHODS

We retrospectively evaluated all 84 patients with late-stage spontaneous osteonecrosis of the knee who had a medial UKA from 1998 to 2005. All patients had preoperative MRI to confirm the diagnosis, exclude metaphyseal involvement, and confirm the absence of major degenerative changes in the lateral and patellofemoral compartments. The mean age of the patients at surgery was 66 years and mean BMI was 28.9. We conducted Kaplan-Meier survival analysis using revision for any reason as the end point. Minimum followup was 63 months (mean, 98 months; range, 63-145 months).

RESULTS

Ten-year survivorship was 89%. Ten revisions were performed; the most common reasons were subsidence of the tibial component (four) and aseptic loosening of the tibial component (three). No patient underwent revision for progression of osteoarthritis in the lateral or patellofemoral compartments.

CONCLUSIONS

Our data suggest spontaneous osteonecrosis of the knee may be an indication for UKA, provided secondary osteonecrosis of the knee is ruled out, preoperative MRI documents the absence of disease in other compartments, and there is no overcorrection in any plane.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Medial unicompartmental knee arthroplasty in patients with spontaneous osteonecrosis of the knee

BACKGROUND

We analyzed the clinical and radiologic results of patients with spontaneous osteonecrosis of the knee treated by minimally invasive medial unicompartmental arthroplasty using Oxford Uni.

METHODS

We reviewed 22 knees in 21 patients which were treated for spontaneous osteonecrosis between 2002 and 2006. Patients included one male and 20 females. The mean age was 70.8 years (range, 53 to 82 years). The mean follow-up period was 70.3 months (range, 48 to 93 months). The clinical results were evaluated using the Hospital for Special Surgery (HSS) knee score and the range of motion of the knee preoperatively and at the final follow-up. Preoperative plain radiographs and magnetic resonance images were analyzed to determine the size and stage of osteonecrotic lesions.

RESULTS

The mean HSS knee score was 64.3 (range, 54 to 75) preoperatively and 92.0 (range, 71 to 100) at the final follow-up. The mean preoperative flexion contracture was 8.9° (range, 0 to 15°) and 0.2° (range, 0 to 5°) at the final follow-up. The mean further flexion increased from 138.6° (range, 100 to 145°) preoperatively to 145.6° (range, 140 to 150°) at the final follow-up. Active full flexion was possible within 2 months of the operation. The squatting position was possible in 16 patients (84.2%) out of 19, except one case of bronchiectasis and one case of spine fracture. The cross-leg posture was possible in 19 patients (90.5%) out of 21. The mean tibiofemoral angle was improved from varus 0.98° to valgus 3.22°. Meniscal bearing dislocation occurred in 2 cases and femoral component loosening occurred in 1 case.

CONCLUSIONS

Unicompartmental knee arthroplasty using Oxford Uni could be an alternative treatment option in spontaneous osteonecrosis of the knee.

Joint-preserving surgical treatment of spontaneous osteonecrosis of the knee

BACKGROUND

To date, reports of surgical treatment of spontaneous osteonecrosis of the knee (SPONK) refractory to non-operative treatment have primarily focused on knee arthroplasty. This report presents an overview of the characteristics of SPONK and reports our experience with joint-preserving surgical treatment of this condition.

METHODS

Fifteen patients who had joint-preserving surgery after failed non-operative modalities were studied. These patients were treated at a single center between January 1998 and September 2006 with a combination of arthroscopy and core decompression, or osteochondral autograft transfers.

RESULTS

Thirteen of the 15 knees (87%) had knee joint survival with a mean Knee Society Score of 81 points (range 45–100 points) at a mean follow-up of 40 months (range 9–120 months). Five of seven knees treated with core decompression had a successful clinical outcome. One of the patients who failed core decompression later underwent osteochondral autograft transfer, and eight of nine knees treated with this modality had a successful outcome.

CONCLUSION

Overall, these results demonstrate that joint-preserving surgical treatment can successfully postpone the need for knee arthroplasty in selected patients with pre-collapse SPONK.

Unicompartmental knee arthroplasty for avascular osteonecrosis

The data analyzing clinical and radiological outcomes after modern unicompartmental knee arthroplasty (UKA) for spontaneous and secondary avascular osteonecrosis are limited. We determined whether: (1) UKA for osteonecrosis was as reliable for alleviating pain and improving function (measured by Knee Society scores) as it is for osteoarthritis, (2) lower limb alignment could be restored after UKA for osteonecrosis, and (3) UKA for osteonecrosis is as durable as UKA for osteoarthritis (measured by survivorship at 12 years). We retrospectively reviewed 30 patients (31 knees) with osteonecrosis; 21 knees had spontaneous osteonecrosis and 10 had secondary osteonecrosis. Mean patient age was 71 years. Clinical and radiological evaluations were performed by an independent observer at a minimum followup of 3 years (mean, 7 years; range, 3-16 years). Reliable pain relief and function improvement were obtained in 30 knees (96%). Restoration of an appropriate lower-limb mechanical axis was achieved for 27 knees (88%). The Kaplan-Meier survivorship was 96.7% at 12 years. Our data suggest UKA is a reasonable solution for restoring clinical function and radiological lower-limb alignment for spontaneous or secondary osteonecrosis limited to one compartment of the knee, with a durable survivorship.

LEVEL OF EVIDENCE

Level IV, retrospective study. See the Guidelines for Authors for a complete description of levels of evidence.

Outcomes of total and unicompartmental knee arthroplasty for secondary and spontaneous osteonecrosis of the knee

BACKGROUND

The reported outcomes of patients who underwent total or unicompartmental knee arthroplasty for secondary and spontaneous osteonecrosis of the knee are often from studies that lack the number of subjects necessary to generate meaningful conclusions. We systematically reviewed the available literature in order to define the outcomes of patients after total knee arthroplasty for secondary osteonecrosis and after total or unicompartmental knee arthroplasty for spontaneous osteonecrosis of the knee.

METHODS

A literature review yielded twenty cohorts with demographic patient information and outcome scores (global knee scores, radiographic outcomes, and revision rates) for patients who had knee arthroplasty as treatment for either secondary or spontaneous osteonecrosis of the knee. The mean preoperative and postoperative global knee scores, the mean revision rate, and the categorization of the mean "poor" and mean "good" outcomes for the knees with each underlying disease were tabulated and reported. The demographic data and the reported mean global knee scores were weighted by the number of knees in each study.

RESULTS

Total knee arthroplasty was performed in 150 knees with secondary osteonecrosis and 148 knees with spontaneous osteonecrosis, and unicompartmental knee arthroplasty was performed in sixty-four knees with spontaneous osteonecrosis. Total knee arthroplasty for spontaneous osteonecrosis of the knee was associated with the best outcomes (higher "good" and postoperative global knee scores and lower revision [3%] and "poor" outcome [6%] rates compared with the other two groups). The outcomes after total knee arthroplasty in knees with secondary osteonecrosis as well as in knees with spontaneous osteonecrosis were better in the cohorts operated on during or after 1985 than in those operated on before 1985. Similarly, the outcomes after unicompartmental knee arthroplasty in knees with spontaneous osteonecrosis of the knee were also better in the cohorts operated on during or after 1985 than in those operated on before 1985.

CONCLUSIONS

Total knee arthroplasty performed as treatment for either secondary osteonecrosis or spontaneous osteonecrosis and unicompartmental knee arthroplasty performed as treatment for spontaneous osteonecrosis were associated with improved outcomes in cohorts with more recent operative dates. The evidence suggests that the use of contemporary cemented implants in total knee arthroplasty and the selective use of stems and augments in patients who have development of secondary osteonecrosis after total knee arthroplasty are producing outcomes that are comparable to those seen after total knee arthroplasty for osteoarthritis. Although the outcomes of patients who have total knee arthroplasty for the treatment of spontaneous osteonecrosis of the knee have historically been favorable, such outcomes have also shown particular improvement in the studies from more recent operative periods. Although poor outcomes were seen after unicompartmental knee arthroplasty in earlier studies of patients with spontaneous osteonecrosis of the knee, it is possible that those results were secondary to inappropriate patient selection, as the authors of the most recent and, to our knowledge, the only study to follow established operative indications regarding the use of unicompartmental knee arthroplasty reported excellent results.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions to Authors on jbjs.org for a complete description of levels of evidence.

Precision of computer-assisted core decompression drilling of the knee

INTRODUCTION

Core decompression by exact drilling into the ischemic areas is the treatment of choice in early stages of osteonecrosis of the femoral condyle. Computer-aided surgery might enhance the precision of the drilling and lower the radiation exposure time of both staff and patients. The aim of this study was to evaluate the precision of the fluoroscopically based VectorVision-navigation system in an in vitro model.

MATERIALS AND METHODS

Thirty sawbones were prepared with a defect filled up with a radiopaque gypsum sphere mimicking the osteonecrosis. 20 sawbones were drilled by guidance of an intraoperative navigation system VectorVision (BrainLAB, Munich, Germany). Ten sawbones were drilled by fluoroscopic control only.

RESULTS

A statistically significant difference with a mean distance of 0.58 mm in the navigated group and 0.98 mm in the control group regarding the distance to the desired mid-point of the lesion could be stated. Significant difference was further found in the number of drilling corrections as well as radiation time needed.

CONCLUSION

The fluoroscopic-based VectorVision-navigation system shows a high feasibility and precision of computer-guided drilling with simultaneously reduction of radiation time and therefore could be integrated into clinical routine.