Computer-assisted surgery in total knee replacement: advantages, surgical procedure and review of the literature.

INTRODUCTION: Total knee replacement (TKR) is one of the most frequent orthopaedic procedures performed every year. At the same time 20% of patients who underwent TKR are not satisfied with the outcome. The reasons are unknown; we think that a mechanical alignment beyond 3° of varus-valgus can represent the most important cause of failure of TKR and consequently patient dissatisfaction. MATERIALS AND METHODS: Neutral mechanical alignment is the main goal in every TKR: this can be achieved through different tools, such as extramedullary and intramedullary guides, patient-specific instrumentation (PSI) and computer-assisted surgery (CAS). The aim of this review is to compare the different alignment techniques in TKR, to describe CAS procedure and CAS results in recent literature. RESULTS: Regarding the intramedullary guide, there is an increased risk of fatty embolism; there are great limitations on its use, or even impossibility, in cases of bone deformity and sequelae of trauma. Regarding the extramedullary guide, it becomes more difficult to use in cases of great obesity or increased soft-tissue volume around the tibia. PSI for TKR has been introduced to improve alignment, reduce outliers, operation time and the risk of fatty embolism by avoidance of intramedullary canal violation. Recent randomized controlled trials and meta-analysis proved no advantage of PSI in improving mechanical axis and implant survivorship. DISCUSSION: CAS has provided to be a useful tool in assisting the surgeon to achieve more accurate post-operative mechanical axis through precise and reproducible bone cuts and ligament balancing. Two meta-analyses definitively proved that CAS technique improves mechanical axis and implant survivorship and one recent meta-analysis demonstrated that CAS provides better mechanical alignment and higher functional scores at short-term follow-up.

Periosteal osteoblastoma of the distal fibula with atypical radiological features: a case report.

We reported the case of a 22 year-old boy who suffered a periosteal osteoblastoma of the distal fibula. The radiographic features of our case did not correlate with the majority of periosteal osteoblastomas of the long bones reported in the literature and were identical to a periosteal aneurysmal bone cyst. Periosteal osteoblastoma is a very rare tumor with a wide range of clinical and radiological features, showing in 15% of cases association with secondary aneurysmal bone cyst. Radiologist and orthopaedic surgeon should be aware of the atypical behavior of this rare entity in order to avoid mistakes with other more common tumors arising on the surface of the long bones.

Intramuscular oxygen-ozone therapy in the treatment of low back pain.

BACKGROUND AND AIM OF THE WORK: Intramuscular paravertebral injections of ozone are minimally invasive, safe and efficacy in reducing pain and disability. The aim of this paper is to present the early results of paravertebral lumbar ozone injections in the treatment of low back pain. METHODS: Between February 2011 and December 2015, a total of 109 patients underwent intramuscular paravertebral lumbar injections of ozone due to low back pain. Of them, 42 interrupted the treatment at a medium of 5.4 injections and were lost to follow-up. Of the 67 remaining patients, only 24 answered to our questionnaire. Local and radiating pain was assessed using a 10-cm horizontal Visual Analogue Scale. Perceived functional status and disability were evaluated using the Oswestry Disability Index, administered before treatment and one month after the last injection. RESULTS: Visual Analogue Scale reduction was demonstrated in 23 out of 29 cycles (79%) of ozone therapy. Regarding disability evaluation, Oswestry Disability Index score reduction was assessed in all except one. No complications were recorded. Our results are similar to the other reports: 79% of patients had VAS reduction of 2.3 points and all except one patient reported ODI reduction (average reduction of 9%). CONCLUSIONS: Lumbar paravertebral oxygen-ozone injections are minimally invasive, safe, cheaper and effective in relieving pain as well as disability. This technique is easy to perform, it doesn't need computed-tomography or anesthesiologist support. We suggest its application in low back pain as first choice to replace intradiscal computed-tomography-guided infiltrations and to avoid or delay surgery.

Bi-unicompartmental versus total knee arthroplasty: long term results.

The purpose is to demonstrate that Bi-Unicom- partmental knee arthroplasty (Bi-Uni) can produce equivalent long-term outcomes to total knee arthroplasty (TKA) in patients with bicompartmental knee osteoarthritis involving both the medial and lateral tibio-femoral compartments. A total of 37 patients with bicompartmental tibio- femoral osteoarthritis of the knee treated between January 1999 and March 2005 underwent either Bi-Uni or TKA. Nineteen patients who underwent simultaneous implantation of 2 unicompartmental knee arthroplasties (UKA) were matched and compared with 18 patients who had undergone a computer assisted TKA. At latest follow-up no statistically significant differences were seen between the 2 patient groups for KSS, Function scores and WOMAC Arthritis Index (pain score). The patients undergoing Bi-Uni did showed a statistically significant superior outcome for function (P < 0.05) and stiffness (P < 0.01) WOMAC indexes compared with the TKA group. The results of this study suggest that Bi-Uni is a valid alternative to address medial and lateral tibio- femoral osteoarthritis of the knee in selected cases. Bi-Uni replacement produces results equivalent TKA in patients with bicompartmental knee osteoarthritis involving both the medial and lateral tibio-femoral compartments and could represent a new frontier in modern knee reconstructive surgery. Level of Evidence: Level IV, retrospective comparative study.

Mazabraud syndrome associated with McCune-Albright syndrome: a case report and review of the literature.

Mazabraud syndrome is a very rare benign disorder characterized by the association of monostotic or polyostotic fibrous dysplasia and one or multiple intramuscular myxomas. McCune -Albright syndrome is a rare benign disorder characterized by the association of polyostotic fibrous dysplasia, cafè-au-lait skin pigmentations and endocrine dysfunction, such as precocious puberty, diabetes mellitus, goiter and breast fibroadenomatosis. The association of Mazabraud syndrome and McCune-Albright in the same patient is an anecdotal event. We report the case of a 28-year-old girl with Mazabraud syndrome associated with McCune-Albright syndrome. Our literature review shows that in these patients there is a higher risk of malignant transformation of fibrous dysplasia into osteosarcoma, confirming previous reports. Conversely, no malignant transformation has been reported for myxomas in isolated Mazabraud syndrome or in the association with McCune-Albright syndrome. We conclude that these patients should be scheduled to a close and long-term follow-up.

Patient-specific modeling of the trochlear morphologic anomalies by means of hyperbolic paraboloids.

Diagnostic and therapeutic purposes are issuing pressing demands to improve the evaluation of the dysplasia condition of the femoral trochlea. The traditional clinical assessment of the dysplasia, based on Dejour classification, recognized 4 increasing (A, B, C, D) levels of severity. It has been extensively questioned in the literature that this classification methodology can be defective suggesting that quantitative measures can ensure more reliable criteria for the dysplasia severity assessment. This study reports on a novel technique to model the trochlear surface (TS), digitally reconstructed by 3D volumetric imaging, using three hyperbolic paraboloids (HP), one to describe the global trochlear aspect, two to represent the local aspects of the medial and lateral compartments, respectively. Results on a cohort of 43 patients, affected by aspecific anterior knee pain, demonstrate the consistency of the estimated model parameters with the morphologic aspect of the TS. The obtained small fitting error (on average lower than 0.80 mm) demonstrated that the ventral aspect of the trochlear morphology can be modeled with high accuracy by HPs. We also showed that HP modeling provides a continuous representation of morphologic variations in shape parameter space while we found that similar morphologic anomalies of the trochlear aspect are actually attributed to different severity grades in the Dejour classification. This finding is in agreement with recent works in the literature reporting that morphometric parameters can only optimistically be used to discriminate between the Grade A and the remaining three grades. In conclusion, we can assert that the proposed methodology is a further step toward modeling of anatomical surfaces that can be used to quantify deviations to normality on a patient-specific basis.

Navigated "small implants" in knee reconstruction.

PURPOSE: At the beginning of this century, unprecedented interest in the concept of using less invasive approaches for the treatment of knee degenerative diseases was ignited. Initial interest in this approach was about navigated and non-navigated knee reconstruction using small implants and conventional total knee arthroplasty. METHODS: To this end, a review of the published literature relating to less invasive compartmental arthroplasty of the knee using computer-based alignment techniques and on soft tissue-dedicated small implants is presented. The authors present and compare their personal results using these techniques with those reported in the current literature. These involved the use of a shorter incision and an emphasis sparing. However, nowadays most surgeons look at compartmental knee resurfacing with the use of small implants as the new customized approach for younger and higher-demand patients. The aim of this paper is to stimulate further debate. RESULTS: Since the beginning of 2000, computer-assisted surgery has been applied to total knee arthroplasty (TKA) and later to compartmental knee arthroplasty. Recent studies in the literature have reported better implant survivorship for younger patients using navigation in TKA at longer-term follow-up. Only one published report was identified showing superior clinical outcomes at short-term follow-up using computer-assisted technology compared with conventional alignment techniques in small implant surgery. No studies were found in the literature that demonstrated similar clinical advantages with navigated small implants at long-term follow-up. Two published meta-analyses were identified reporting better implant and limb alignment and no increase in complications using a navigated unicompartmental knee arthroplasty. However, neither meta-analysis showed superior clinical outcomes or survivorship with the navigated techniques. CONCLUSION: In conclusion, we can assert that replacing just the damaged compartment and preserving the normal biomechanics will require not only new implant designs but also new technologies allowing the surgeon to make extremely precise adjustments to implant alignment and providing continuous feedback during surgery. LEVEL OF EVIDENCE: IV.

Synovial chondrosarcoma.

BACKGROUND: Synovial chondrosarcoma (SCH) is a very rare tumor arising in the intra-articular cavity. In the majority of literature reports it is described as a malignant transformation of a pre-existing synovial chondromatosis (SC). We reported a systematic review of primary and secondary SCH described in the literature with the aim to recollect data from different case-reports and case-series, trying to summarize general aspects of this very rare disease. METHODS: We collected 42 abstracts in the form of case series and case reports, which reported 67 cases of SCH. Studies were taken into account only if they proved a histological diagnosis of SCH, either primary or secondary, with or without evidence of pre-existing SC. RESULTS: The average age of SCH was 56.9 years, with prevalence for male sex. The average time of malignant transformation was 11.2 years. The most affected joint was the knee (47.7%), followed by hip (34.3%) and ankle (5.9%). SCH was described as de novo sarcoma only in 13 cases (19%). Surgery ended up with amputation in 59.7% of cases. Local recurrence rate was 28.3%. CONCLUSIONS: We concluded that prognosis of SCH is worse than conventional one and we speculated this is due to the difficult site of the tumor (intraarticular), diagnostic delay and inappropriate previous treatments. We consider that a rapid deterioration of a SC or rapid recurrence after synoviectomy should be considered suspicious of malignant transformation and should be treated in a reference center.

A flat all-polyethylene tibial component in medial unicompartmental knee arthroplasty: a long-term study.

PURPOSE: The aim of this study is to present the clinical and radiological results of a cemented unicompartmental knee arthroplasty (UKA) using a flat all-polyethylene tibial component at long-term follow-up, in a homogeneous group of patients with medial femoro-tibial knee arthritis. METHODS: The study group included 53 knees in 51 patients who were treated between January 1998 and November 1999 using a flat all-polyethylene tibial component. The same surgical technique was used for all patients. Inclusion criteria included a diagnosis of atraumatic arthritis, pre-operative flexion greater than 100° with no flexion deformity, a varus deformity of less than 10°, and a body mass index (BMI) less than 35. A neutral mechanical axis was considered the end-point in all interventions. The patients were assessed clinically using the International Knee Society (IKS) and the functional scores at follow-up. Plain radiographs were used to determine the alignment of the mechanical axis at 5, 10 and 14.7-year follow-up. A radiographic analysis of loosening, based on the method described by the IKS, was performed and the degree of arthritic progression in the non-resurfaced compartment was also assessed. RESULTS: At latest follow-up five patients had died and the data for three patients had not been collected. At final review four knees had undergone revision surgery and a further patient had declined a recommended revision TKA. The main indication for revision surgery was progressive aseptic loosening of the tibial component in female patients. No revisions were required because of arthritic progression in the lateral compartment. Over time the clinical outcomes did not show statistically significant differences. There was a significant worsening of the mechanical axis at the last follow-up compared with the results at five and ten year review. CONCLUSIONS: This study demonstrated that, in primary arthritis involving the medial femoro-tibial compartment, UKA using a flat all-polyethylene component could be considered an effective surgical option. Attention should be paid to progressive worsening of the mechanical axis over time associated with progressive radiolucency especially in female patients. LEVEL OF EVIDENCE: IV.

Patellofemoral joint replacement, an evolving concept.

Isolated patellofemoral arthritis is a rare disease, whose management is challenging and controversial. Patellofemoral joint replacement can be an effective treatment for this condition. The very concept of a patellofemoral implant has evolved throughout the years, resulting in more anatomic designs and reproducible surgical techniques. The clinical outcomes of this procedure are strictly related to surgical indications, implant design and appropriate surgical technique.

Automating the design of resection guides specific to patient anatomy in knee replacement surgery by enhanced 3D curvature and surface modeling of distal femur shape models.

Personalized resection guides (PRG) have been recently proposed in the domain of knee replacement, demonstrating clinical outcome similar or even superior to both manual and navigated interventions. Among the mandatory pre-surgical steps for PRG prototyping, the measurement of clinical landmarks (CL) on the bony surfaces is recognized as a key issue due to lack of standardized methodologies, operator-dependent variability and time expenditure. In this paper, we focus on the reliability and repeatability of an anterior-posterior axis, also known as Whiteside line (WL), of the distal femur proposing automatic surface processing and modeling methods aimed at overcoming some of the major concerns related to the manual identification of such CL on 2D images and 3D models. We show that the measurement of WL, exploiting the principle of mean-shifting surface curvature, is highly repeatable and coherent with clinical knowledge.

Post traumatic knee arthritis: navigated total knee replacement without hardware removal.

BACKGROUND: The Authors present the results of a series of navigated total knee replacements (TKR) without hardware removal in patients with post-traumatic arthritis following femoral fractures. The purpose of the paper was to determine the effectiveness of computer-assisted TKR in these patients compared to routine primary implants. METHODS: Sixteen patients with post-traumatic knee arthritis following a distal femoral fracture and retained hardware were included in the study (group I). Patients in the study group were matched with patients who had undergone a computer navigated TKR using the same implant and software (group II). The indication for TKR in all group II patients was atraumatic arthritis and surgery was performed in the same period as the study group. Patients were matched for age, gender, pre-operative range of motion, severity of arthritis pre-operatively, type and grade of deformity and implant features. RESULTS: There were no statistically significant differences in surgical time, hospital staying or intra-operative and post-operative complications between the two study groups. At the latest follow-up no statistically significant difference was seen for the Knee Society Score and WOMAC indices. Implant alignment and radiological parameters were similar in both groups. CONCLUSIONS: This study demonstrated that post-traumatic knee arthritis following prior distal femoral fracture can be safely managed using a computer navigated TKR without hardware removal. Comparison between this patient group and a matched group with atraumatic arthritis showed similar post-operative results and complication rates. LEVEL OF EVIDENCE: III.

Computer-assisted unicompartmental knee arthroplasty using dedicated software versus a conventional technique.

PURPOSE: The aim of this study was to retrospectively compare the results of two matched-paired groups of patients who had undergone a medial unicompartmental knee arthroplasty (UKA) performed using either a conventional or a non-image-guided navigation technique specifically designed for unicompartmental prosthesis implantation. METHODS: Thirty-one patients with isolated medial-compartment knee arthritis who underwent an isolated navigated UKA were included in the study (group A) and matched with patients who had undergone a conventional medial UKA (group B). The same inclusion criteria were used for both groups. At a minimum of six months, all patients were clinically assessed using the Knee Society Score (KSS) and the Western Ontario and McMaster Osteoarthritis Index (WOMAC) index. Radiographically, the frontal-femoral-component angle, the frontal-tibial-component angle, the hip-knee-ankle angle and the sagittal orientation of components (slopes) were evaluated. Complications related to the implantation technique, length of hospital stay and surgical time were compared. RESULTS: At the latest follow-up, no statistically significant differences were seen in the KSS, function scores and WOMAC index between groups. Patients in group B had a statistically significant shorter mean surgical time. Tibial coronal and sagittal alignments were statistically better in the navigated group, with five cases of outliers in the conventional alignment technique group. Postoperative mechanical axis was statistically better aligned in the navigated group, with two cases of overcorrection from varus to valgus in group B. No differences in length of hospital stay or complications related to implantation technique were seen between groups. CONCLUSION: This study shows that a specifically designed UKA-dedicated navigation system results in better implant alignment in UKA surgery. Whether this improved alignment results in better clinical results in the long term has yet to be proven.

Spontaneous patella fracture associated with anterior tibial tubercle pseudarthrosis in a revised knee replacement following knee arthrodesis.

BACKGROUND: Conversion of a knee arthrodesis to a Total Knee Arthroplasty is an uncommon procedure. Revision Total Knee Arthroplasty in this setting presents the surgeon with a number of challenges including the management of the extensor mechanism and patella. CASE PRESENTATION: We describe a unique case of a 69 years old Caucasian man who underwent a revision Total Knee Arthroplasty using a tibial tubercle osteotomy after a previous conversion of a knee arthrodesis without patella resurfacing. Unfortunately 9 months following surgery a tibial tubercle pseudarthrosis and spontaneous patella fracture occurred. Both were managed with open reduction and internal fixation. At 30 months follow-up the tibial tubercle osteotomy had completely consolidated while the patella fracture was still evident but with no signs of further displacement. The patient was completely satisfied with the outcome and had a painless range of knee flexion between 0-95°. CONCLUSIONS: We believe that patients undergoing this type of surgery require careful counseling regarding the risk of complications both during and after surgery despite strong evidence supporting improved functional outcomes.

An uncommon cause of cemented unicompartmental knee arthroplasty failure: fracture of metallic components.

PURPOSE: Despite good overall clinical results, unicompartmental knee replacements (UKR) are not without their problems and failures have been reported. The most common causes of UKR failure are component loosening, poor patient selection, poor surgical technique, polyethylene wear and progression of arthritis in other compartments. The purpose of this study is to present a series of atraumatic fractures of metallic components in a UKR treated in a single orthopaedic centre. METHOD: Since 1999, 121 failed unicompartmental knee arthroplasties have been referred to our centre. In six of these, atraumatic breakage of a metal component in the cemented UKR was seen and included in this study. Pre-operative alignment, BMI and implant longevity were documented. The femoral implant failed in 4 patients and the tibial implant in a further 2. RESULTS: All the femoral implant fractures occurred within 3 years of UKR surgery (mean: 22.2 months, SD: 10.6 months). Tibial implant breakage occurred at a mean of 8.5 years (SD: 2.4 months) following UKR. All patients were treated with conversion to a navigated total knee replacement. A primary total knee arthroplasty was used in all cases with one patient requiring a tibial component incorporating a wedge and stem following breakage of the original UKR tibial implant. CONCLUSION: Fracture of the metallic components is a potential cause of failure of unicompartmental knee arthroplasty. In our experience, the incidence of this complication was 4.9 % of all UKR failures. Patients with a BMI greater than 30 and a progressive deterioration in limb alignment were at greater risk.

Computer-assisted total knee arthroplasty after prior femoral fracture without hardware removal.

This study presents a consecutive series of patients who underwent total knee arthroplasty (TKA) after prior distal femoral fracture without hardware removal. The purpose of this study was to determine the effectiveness of computer-assisted TKA in patients with posttraumatic arthritis, specifically those with retained hardware after prior distal femoral fracture. The study group included a consecutive series of 16 patients who had developed posttraumatic knee arthritis after a distal femoral fracture with retention of hardware (group A). Patients in the study group were matched with patients who had undergone a computer-assisted TKA using the same implant and software (group B). The indication for TKA in all group B patients was atraumatic arthritis, and surgery was performed during the same period as that in the study group. Patients were matched for age, sex, preoperative range of motion, preoperative severity of arthritis, type and grade of deformity, and implant features. No statistically significant differences existed between the 2 study groups in terms of operative time, duration of hospital stay, or intra- and postoperative complications. At last follow-up, no statistically significant differences existed in Knee Society Scores and Western Ontario and McMaster Universities Arthritis Index scores. Implant alignment and radiological parameters were similar in both groups. This study demonstrated that posttraumatic knee arthritis after prior distal femoral fracture can be safely managed using a computer-assisted TKA without hardware removal. Comparison between the study group and a matched group with atraumatic arthritis showed similar postoperative results and complication rates.

Is computer-assisted total knee replacement for beginners or experts? Prospective study among three groups of patients treated by surgeons with different levels of experience.

BACKGROUND: Computer-assisted total knee replacement (TKR) has been shown to improve radiographic alignment and therefore the clinical outcome. Outliers with greater than 3° of varus or valgus malalignment in TKR can suffer higher failure rates. The aim of this study was to determine the impact of experience with both computer navigation and knee replacement surgery on the frequency of errors in intraoperative bone cuts and implant alignment, as well as the actual learning curve. MATERIALS AND METHODS: Three homogeneous groups who underwent computer-assisted TKR were included in the study: group A [surgery performed by a surgeon experienced in both TKR and computer-assisted surgery (CAS)], B [surgery performed by a surgeon experienced in TKR but not CAS], and C [surgery performed by a general orthopedic surgeon]. In other words, all of the surgeons had different levels of experience in TKR and CAS, and each group was treated by only one of the surgeons. Cutting errors, number of re-cuts, complications, and mean surgical times were recorded. Frontal femoral component angle, frontal tibial component angle, hip-knee-ankle angle, and component slopes were evaluated. RESULTS: The number of cutting errors varied significantly: the lowest number was recorded for TKR performed by the surgeon with experience in CAS. Superior results were achieved in relation to final mechanical axis alignment by the surgeon experienced in CAS compared to the other surgeons. However, the total number of outliers showed no statistically significant difference among the three surgeons. After 11 cases, there were no differences in the number of re-cuts between groups A and C, and after 9 cases there were no differences in surgical time between groups A and B. CONCLUSION: A beginner can reproduce the results of an expert TKR surgeon by means of navigation (i.e., CAS) after a learning curve of 16 cases; this represents the break-even point after which no statistically significant difference is observed between the expert surgeon and the beginner utilizing CAS.

Mean-shifted surface curvature algorithm for automatic bone shape segmentation in orthopedic surgery planning: a sensitivity analysis.

The results of recent studies concerning statistical bone atlases and automated shape analysis are promising with a view to widening the use of surface models in orthopedic clinical practice, both in pre-operative planning and in the intra-operative stages. In this domain, automatic shape analysis is strongly advocated because it offers the opportunity to detect morphological and clinical landmarks with superior repeatability in comparison to human operators. Surface curvatures have been proposed extensively for segmentation and labeling of image and surface regions based on their appearance and shape. The surface curvature is an invariant that can be exploited for reliable detection of geometric features. In this paper, we investigate the potentiality of the algorithm termed mean-shift (MS), as applied to a non-linear combination of the minimum and maximum curvatures of a surface. We exploited a sensitivity analysis of the algorithm parameters across increasing surface resolutions. Results obtained with femur and pelvic bone surface data, reconstructed from cadaveric CT scans, demonstrated that the information content derived by the MS non-linear curvature overcomes both the mean and the Gaussian curvatures and the original non-linear curvature. By applying a threshold-based clustering algorithm to the curvature distribution, we found that the number of clusters yielded by the MS non-linear curvature is significantly lower (by a factor of up to 6) than that obtained by using the original non-linear curvature. In conclusion, this study provides valuable insights into the use of surface curvature for automatic shape analysis.

Advanced computational framework for the automatic analysis of the acetabular morphology from the pelvic bone surface for hip arthroplasty applications.

2D- and 3D-based innovative methods for surgical planning and simulation systems in orthopedic surgery have emerged enabling the interactive or semi-automatic identification of the clinical landmarks (CL) on the patient individual virtual bone anatomy. They enable the determination of the optimal implant sizes and positioning according to the computed CL, the visualization of the virtual bone resections and the simulation of the overall intervention prior to surgery. The virtual palpation of CL, highly dependent upon the examiner's expertise, was proved to be time consuming and to suffer from considerable inter-observer variability. In this article, we propose a fully automatic algorithmic framework that processes the pelvic bone surface, integrating surface curvature analysis, quadric fitting, recursive clustering and clinical knowledge, aiming at computing the main parameters of the acetabulum. The performance of the method was evaluated using pelvic bone surfaces reconstructed from CT scans of cadavers and subjects with pathological conditions at the hip joint. The repeatability error of the automated computation of acetabular center, size and axis parameters was less than 1 mm, 0.5 mm, and 1.5°, respectively. The computed parameters were in agreement (<1.5 mm; <0.5 mm; <3.0°) with the corresponding reference parameters manually identified in the original datasets by medical experts. According to our results, the proposed method is put forward to improve the degree of automation of image/model-based planning systems for hip surgery.