The Oxford unicompartmental knee prosthesis: an independent 10-year survival analysis

One hundred forty-nine medial prostheses were implanted in 140 patients between 1988 and 1996. After a mean of 67 months 28 patients had died, without the need for revision. Seventeen prostheses were lost to follow-up. Revision surgery using a total knee prosthesis was performed in 16 cases. In four others, a lateral prosthesis was implanted subsequently to a medial one. One of these four was revised to a total knee prosthesis 6 years later. In another four cases, late complications of the meniscal bearing were treated with replacement of this bearing. The surviving prostheses were seen back after a mean of 126 months. The cumulative survival rate at 10 years was 82% for the whole population and 84% when knees with a previous high tibial osteotomy were excluded. Since these results compare poorly to the survival of total knee arthroplasty, this prosthesis is not the first-choice implant. Because it preserves a maximum of bone stock and is revised to a total prosthesis almost without difficulty, it is the first-choice implant for medial unicompartmental osteoarthritis in patients younger than 65. Further research is mandatory to confirm that this prosthesis very rarely needs revision in patients older than 75. It should not be used in osteotomized knees.     

The Oxford unicompartmental knee prosthesis: a 5-year follow-up

We present our medium-term results with the Oxford unicompartmental knee prosthesis for unicompartmental osteoarthrosis. After an average of 58 months the mean on the Hospital for Special Surgery knee score in 38 medial and 3 lateral prostheses (39 patients) was 87. There were three revisions; in the remaining 36 patients the results were: 29 excellent, 3 good, 2 moderate, and 2 poor. In two of the three revisions and in two of the four poor and moderate results, the indications for the procedure were debatable. Our findings confirm the good results reported in other studies and underline the importance of adhering to strict indications to reduce the number of poor results. Received: 12 July 1999/Accepted: 5 January 2000     

Free bone cement fragments after minimally invasive unicompartmental knee arthroplasty: an underappreciated problem

The minimally invasive implantation of unicompartmental knee arthroplasty (UKA) leads to excellent functional results, but due to the reduced intraoperative visibility the removal of excessive cement may be difficult. In a retrospective study we assessed radiologically the incidence of loose and excess bone cement in 120 UKAs and correlated it to the thickness of the tibial cement layer. In 25 cases loose or attached excess cement was seen. Two of these patients with loose cement bodies required revision surgery. An additional 2 patients not operated at our institution required revision because of pain and loss of motion. The average thickness of the tibial cement layer was 3.1 (1.7-5.0) mm in all the patients. But it was significantly higher in the group with excess cement bodies [3.3 (2.3-5.0) mm] compared to the group without excess cement [3.0 (1.7-4.1) mm] (P < 0.05). Symptomatic free cement bodies need to be removed immediately, if necessary arthroscopically, in order to avoid damage to the implants. To avoid this problem in minimally invasive UKA, intraoperative fluoroscopy, a dental mirror or a nerve hook seem to be useful tools to identify and remove loose or excess cement.     

The Oxford phase III unicompartmental knee replacement in patients less than 60 years of age

Treatment of younger patients with medial unicompartmental disease of the knee joint remains a challenging therapeutic dilemma. With the refinement of implant design, fixation and the minimally invasive techniques employed with unicompartmental knee replacement, indications have expanded to include its use in young patients. A prospective cohort of 46 unicompartmental knee procedures were performed with a 2-year minimum and 6-year maximum follow-up, using the Oxford phase III unicompartmental knee arthroplasty, in the younger patient group (age 60 or younger). We conclude that the unicompartmental knee arthroplasty is an important option for the treatment of medial compartment disease for patients 60 years or younger. Obesity can cause technical difficulties, increased risk of complications and early failure of this prosthesis.     

Participation in sporting activities following knee replacement: total versus unicompartmental

Few studies have been published assessing patients sporting activity after total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA). Common concerns of patients undergoing TKA or UKA are whether they can continue with sporting activities after surgery. This study compares the sporting activity of TKA and UKA patients preoperatively and postoperatively. A total of 110 patients were surveyed by questionnaire. Seventy-six patients had undergone TKA and 34 patients had undergone UKA. They were assessed for their participation in low-impact sport preoperatively and postoperatively at a mean follow up of 21.6 +/- 5.3 and 22.3 +/- 7.8 months, respectively. Low-impact sports are those which a surgeon would expect patients to be able to participate in postoperatively. Data were separately analysed for older and younger patients and women and men, respectively. The results were as follows: before surgery, 55 of 76 patients in the TKA group participated in an average of 1.3 different sports and postoperatively, 35 of 76 patients participated in an average of 0.7 different sports. In the UKA group, 30 of 34 patients participated in an average of 1.5 different sports preoperatively and postoperatively, 29 of 34 patients participated in an average of 1.4 different sports. The return to sport rate was 96.7% in the UKA group and 63.6% in the TKA group. In the TKA group, the average frequency of sport preoperatively was 3.0 sessions per week (62.7 min) and postoperatively it decreased to 2.0 sessions per week (37.5 minutes). In the UKA group, the average frequency of sport preoperatively was 3.2 sessions per week (85.0 min) and postoperatively it increased to 3.4 sessions per week (92.1 min). The average time before resuming sport after surgery was 4.1 months in the TKA group and 3.6 months in the UKA group; 42.9% of patients in the TKA group and 24.1% of patients in the UKA group reported pain during sports after surgery; 80.3% of the patients in the TKA group and 88.2% of the patients in the UKA group felt that surgery had increased or maintained their sporting ability. Oxford knee scores decreased significantly one year after surgery in both the TKA group and the UKA group. In conclusion, the patients in our study had a significantly greater return to sport rate after UKA than patients who had undergone TKA. A large proportion of patients in the TKA group did not return to sport which their surgeon would have expected them to including golf and bowls. Patients in the UKA group also took part in more sporting sessions and for a longer period of time than patients in the TKA group. Moreover, patients undergoing UKA also returned to sport more quickly than patients undergoing TKA.     

Comparative study of the use of computer assisted navigation system for axial correction in medial unicompartmental knee arthroplasty

The aim of our study was to compare the use of the Orthopilot Navigation system with conventional non-navigation technique for medial UKA with respect to the intraoperative mechanical limb alignment measurements and correlation with the postoperative radiological measurements. The postoperative mechanical limb alignment axes of 51 consecutive medial unicompartmental knee arthroplasty performed by a single surgeon over a 12-month period were measured. The cases were randomly assigned to two groups of which 21 cases were performed using conventional non-navigation based technique and 30 cases were performed using the Orthopilot Navigation System. Computed tomography (CT) scanogram was performed for all cases within the same hospitalization stay to assess the postoperative mechanical limb alignment. Our results showed that the non-navigated group had a more neutral mechanical axis with a narrower range compared to the navigation assisted group. The difference in the mean mechanical axis between the two groups was statistically not significant. There was poor correlation between the intraoperative navigation system measurements and the postoperative radiological measurements. In conclusion, the use of computer navigation in UKA is not as well validated as compared to TKA. We did not demonstrate any improvement in postoperative axial limb alignment measurement in using a computer navigation system compared to conventional non-navigation technique.     

Preliminary remarks on a prospective multicenter study of the Repicci minimally invasive unicondylar knee replacement

Prospective multicentric study on unicondylar knee arthroplasties using the minimally invasive method described by Repicci. Three hundred and seventy nine unicondylar knee arthroplasties in patients with an average age of 66 years were examined preoperatively and 40 weeks postoperatively. In 98.4% of the cases the medial compartment was replaced. The examination was documented using the Knee Society Score (KSS). Radiological examination was done using films of the knee in two planes in standing position and a long leg axis film. The mean KSS increased significantly (P<0.005) from 100.1 (SD 21.7) before surgery to 179.1 (SD 24.0) postoperatively. Ninety-five of the patients were subjectively satisfied with the procedure. Using correlation analysis, we found that osteoarthritic changes of the patella had a highly significant (p=0.001) influence on the KSS results. Patients age and the pain subscale of the KSS also had a highly significant (p=0.01) influence on the KSS result. Short-term results of the Repicci unicondylar arthroplasty using the minimally invasive technique are encouraging in terms of patient satisfaction. It became apparent that osteoarthritic changes of the patella, flexion contractures and extension deficits have a considerable influence on the overall result.     

Fracture of the femoral component of a Brigham unicompartmental knee: a case report

We report the failure of a femoral component in a unicompartmental knee replacement 6 years after implantation. The implant fractured 15 mm from the anterior tip, and scanning electron microscopy confirmed fatigue to be the cause of failure. The clinical and laboratory findings are presented, and the causes and implications of this mode of implant failure are discussed.     

Minimally invasive unicompartmental knee replacement: retrospective clinical and radiographic evaluation of 83 patients

We performed a retrospective clinical and radiographic evaluation of 83 nonconsecutive patients operated in our institute between February 1996 and March 2003 with a mean follow-up of 60 months to assess the efficiency of unicompartmental knee replacement (UKR) performed with a minimally invasive technique. The aim of this study was to correlate the clinical outcome with the pre- and post-operative alignment and with implant positioning on coronal and sagittal plane. Eighty-three nonconsecutive patients (60 males, 23 females) underwent cemented UKR (De Puy Preservation Uni with all-poly tibial component), for both medial OA (80 patients) and AVN of the medial femoral condyle (3 patients). All patients were available at final follow-up evaluation, and they all presented an evident varus alignment at pre-operative clinical and radiographic evaluation. At radiographic measurement, we considered a knee with femoro-tibial angle (FTA) > 175° as varus knee, 170° < FTA < 175° as normal knee and a knee with a FTA < 170° as a valgus knee. Moreover, we considered a tibial plateau angle (TPA) > 90° for valgus knee and a TPA < 90° for varus knee. According to Hospital for Special Surgery (HSS) scoring system, at a mean follow-up of 60 months, 61 (74%) cases were excellent (100-85 points), 15 (18%) cases were good (84-70 points) and 7 cases (8%) had fair results (<70 points). In our series, patients with an excellent clinical result presented a mean varus deformity of 7.2° (3.6°–10.8°) pre-operatively. According to literature, we demonstrated that a small amount of undercorrection with a small amount of residual varus deformity of 3°–5° is the goal to be reached in order to avoid both rapid degeneration of the nonreplaced compartment and the premature loosening of the replaced compartment. We performed a mean axial correction of 5° (SD 3.9°), leaving a mean axial varus deformity of 2.2° in the excellent group. In our series, the group with excellent results also showed a post-operative PTS of 7° (2.4°–11.6°), while mean pre-operative PTS was 6.5° (2.7°–10.3°). In this study, results have shown that minimally invasive UKR producing a small amount of varus undercorrection in selected patients with medial tibio-femoral osteoarthritis or moderate avascular necrosis of the medial femoral condyle provides excellent clinical and functional results. Overcorrection of varus malalignment with a UKR may produce both rapid degeneration of the lateral tibio-femoral compartment and the early failure of the replaced compartment.     

Staged bilateral mobile-bearing and fixed-bearing total knee arthroplasty in the same patients: a prospective comparison of a posterior-stabilized prosthesis

Mobile-bearing total knee arthroplasty (TKA) has several theoretical advantages over fixed-bearing TKA. We conducted a prospective randomized trial to compare the results of mobile-bearing and fixed-bearing posterior-stabilized TKA in the same patients using the same femoral component design of a mobile-bearing prosthesis in one knee and a fixed-bearing prosthesis in the other knee in 25 patients with osteoarthritis. The mean follow-up was 40 months. No significant differences were found in the mobile-bearing and fixed-bearing knees in terms of clinical and radiographic results. No osteolysis, loosening, or revision occurred. One knee with a mobile-bearing prosthesis had a dislocation of the rotating bearing; however, spontaneous reduction occurred and the dislocation did not recur. Satisfactory early results can be achieved in both mobile-bearing and fixed-bearing knees. We could not demonstrate an advantage of a mobile-bearing TKA.     

Clinical and functional results after the rehabilitation period in minimally-invasive unicondylar knee arthroplasty patients

The objective of the present study was to analyze the clinical and functional outcome after minimally-invasive implantation of a Repicci-type unicompartmental sledge prosthesis . In 29 patients with primary unicompartmental knee osteoarthritis, 29 replacements of the medial compartment and four of the lateral compartment were performed using the minimally-invasive technique with the metal-backed and the all-polyethylene versions of the Repicci sledge prosthesis. Electromyography (EMG) of standardized locations was measured with the MyoSystem 2000 and analyzed with Myoresearch software. Gait analysis was performed with a six-camera motion analysis system and force platforms. Established clinical and quality of life (SF-36) scores were used to compare patients with 11 healthy age-matched individuals. The Repicci sledge prosthesis led postoperatively to functional results that were in the range of healthy joints, and superior to sledge prostheses of a different design. Gait and balance parameters were comparable to the control group, whilst electromyographically lower amplitudes were found in the patients than the controls and in the operated legs as compared to the non-operated legs. Many parameters of quality of life and activity were comparable to age-matched healthy individuals, and quality of life was superior to total knee replacement. When implanted using a minimally-invasive technique and with suitable patient selection, the Repicci sledge led to functional results comparable to those of healthy joints and gait parameters comparable to those of healthy individuals. The level of evidence is Level III, retrospective cohort study.     

Minimal invasive and computer assisted total knee replacement compared with the conventional technique: a prospective, randomised trial

Minimal invasive surgery (MIS) in total knee replacement (TKR) has been favoured by several authors and the industry and is asked for by the patients. Computer assisted surgery (CAS) is proposed to support the surgeon in terms of postoperative leg alignment and implant orientation. To prove the hypothesis that MIS in TKR fastens early rehabilitation compared to the standard approach and that CAS–MIS in TKR improves accuracy in implant position compared to the freehand MIS and freehand standard technique, we performed a prospective, randomised short-term trial which was approved by the local ethic committee. In total, 90 patients underwent TKR. The conventional group (n = 30) underwent conventional TKR, the MIS group (n = 30) underwent MIS–TKR without navigation, the CAS–MIS group (n = 30) underwent TKR using navigation and the MIS approach. Groups were comparable regarding patients’ specific parameters. The length of incision in extension was significantly lower in the MIS (13.2 cm) and CAS–MIS technique (12.9 cm) compared to the conventional technique (17.3 cm) (P < 0.01). Knee Society and WOMAC Score were similar in all three groups after 1, 6 and 12 weeks, no significant differences were seen between groups at any point of time. Postoperative deviation of the mechanical leg axis was significantly better in the CAS–MIS group compared to the conventional group and the MIS one (P < 0.05). The clinical relevance of our results is that the benefit of the minimal invasive approach in TKR is still not proven and navigation improves postoperative accuracy of leg alignment and component orientation. Our study shows that for the group of patients included there is no statistically significant difference in early rehabilitation between MIS and the conventional approach based on the Knee Society and WOMAC Score. Using the CAS technique restoration of leg axis was more accurate. Level of evidence: Therapeutic Level I. Prospective randomised.     

Comparison of gait kinematics in patients receiving minimally invasive and traditional hip replacement surgery: a prospective blinded study

Minimally invasive (MI) total hip replacement (THR) supposedly provides improved ambulation in the immediate post-operative period. This study used a prospective blinded design to analyse early post-operative walking ability using gait analysis. Seventeen patients were available for full analysis with nine having had the MI technique and eight having the standard incision (SI) technique. Patients were blinded as to the incision used, as were all physiotherapists and assessors. Differences in temporal-spatial variables and joint kinematics measured 1 day pre-operatively, 2 days post-operatively and 42 days (6 weeks) post-operatively were compared between groups. There was no significant difference in velocity, step length of the affected or unaffected leg, stride length or stance phase duration between the MI and SI groups between any of the timepoints tested. There was no significant improvement in the gait kinematics of the MI group compared to the SI group either 2 days post-operatively or 6 weeks post-operatively. Contrary to previous studies, there was no improvement in early post-operative gait for those patients who received THR using the minimally invasive technique.     

Operative management of the medial collateral ligament in the multi-ligament injured knee: an evidence-based systematic review

While it is generally accepted that most partial and isolated medial collateral ligament (MCL) injuries can be treated non-operatively, ideal treatment of the MCL in multi-ligament knee injuries remains controversial. High failure rates with repair of the posterolateral corner in the multi-ligament injured knee have been recently reported, favoring reconstruction instead. The same maybe true for MCL injuries, however evidence-based treatment recommendations are lacking in the current orthopedic literature. The purpose of this study was to perform an evidence-based systematic review of the operative management (repair and/or reconstruction) of the MCL in the setting of multi-ligament knee injuries. A comprehensive search of MEDLINE and the Cochrane databases for all relevant articles published in English from 1978 to 2008 on the outcomes of surgical management (repair and/or reconstruction) of the MCL in the setting of combined ligament injuries was performed. Inclusion criteria included articles published in (1) English, (2) on human subjects, (3) between the years of 1978 and 2008, (4) had minimum 12-month follow-up, with a mean of at least 24 months, (5) on surgical management of MCL injuries, (6) associated with multi-ligament injuries (three or more ligaments) and/or knee dislocation, and (7) reported objective outcome data on the respective patient cohorts. Exclusion criteria consisted of technique papers, case reports, studies that included fractures associated with MCL injury and those that included pediatric patients. The review identified eight relevant studies. Five articles focused on MCL repair, while three articles focused on MCL reconstruction. No prospective studies compared MCL repair or reconstruction with non-operative treatment or directly compared MCL reconstruction with MCL repair. Currently there is a paucity of objective data on the outcomes regarding surgical management of MCL tears in the combined ligament injured knee. This systematic review demonstrated satisfactory results in both repair and reconstruction groups. Future objective outcome-based studies as well as comparative studies are needed to further evaluate the optimal treatment modality before evidence-based recommendations can be made. Therefore, individual treatment decisions for each patient should be based on the characteristics and nature of the injury.     

Fast magnetic resonance imaging of the knee using a parallel acquisition technique (mSENSE): a prospective performance evaluation

The performance of a magnetic resonance (MR) imaging strategy that uses multiple receiver coil elements and integrated parallel imaging techniques (iPAT) in traumatic and degenerative disorders of the knee and to compare this technique with a standard MR imaging protocol was evaluated. Ninety patients with suspected internal derangements of the knee joint prospectively underwent MR imaging at 1.5 T. For signal detection, a 6-channel array coil was used. All patients were investigated with a standard imaging protocol consisting of different turbo spin-echo sequences proton density (PD), T₂-weighted turbo spin echo (TSE) with and without fat suppression) in three imaging planes. All sequences were repeated with an integrated parallel acquisition technique (iPAT) using the modified sensitivity encoding (mSENSE) algorithm with an acceleration factor of 2. Two radiologists independently evaluated and scored all images with regard to overall image quality, artefacts and pathologic findings. Agreement of the parallel ratings between readers and imaging techniques, respectively, was evaluated by means of pairwise kappa coefficients that were stratified for the area of evaluation. Agreement between the parallel readers for both the iPAT imaging and the conventional technique, respectively, as well as between imaging techniques was found encouraging with inter-observer kappa values ranging between 0.78 and 0.98 for both imaging techniques, and the inter-method kappa values ranging between 0.88 and 1.00 for both clinical readers. All pathological findings (e.g. occult fractures, meniscal and cruciate ligament tears, torn and interpositioned Hoffa’s cleft, cartilage damage) were detected by both techniques with comparable performance. The use of iPAT lead to a 48% reduction of acquisition time compared with standard technique. Parallel imaging using mSENSE proved to be an efficient and economic tool for fast musculoskeletal MR imaging of the knee joint with comparable diagnostic performance to conventional MR imaging.Karl-Friedrich Kreitner and Bernd Romaneehsen contributed equally to this work.     

Spiral CT arthrography of the knee: technique and value in the assessment of internal derangement of the knee

Computed tomography imaging has achieved excellent multiplanar capability and submillimeter spatial resolution due to the development of the spiral acquisition mode and multidetector row technology. Multidetector spiral CT arthrography (CTA) yields valuable information for the assessment of internal derangement of the joints. This article focuses on the value of spiral CTA of the knee in the assessment of the meniscus, anterior cruciate ligament, and hyaline cartilage lesions. Advantages and disadvantages of spiral CTA with respect to MR imaging are presented.     

MR imaging of the knee in patients with medial unicompartmental arthroplasty: comparison among sequences at 1.5 T

Purpose

This study was done to test a series of magnetic resonance (MR) imaging sequences of the knee after medial unicompartmental arthroplasty.

Materials and methods

Four patients who had undergone Oxford III medial unicompartmental arthroplasty underwent 1.5-T MR imaging of the operated knee using coronal sequences: T1-weighted spin-echo (SE), T1-weighted turbo SE (TSE), proton-density (PD)- and T2-weighted TSE, T1-weighted gradient echo (GE), short-tau inversion recovery (STIR), multi echo data image combination (MEDIC), T2*-weighted GE, volumetric interpolated breath-hold examination (VIBE), and dual-echo steady state (DESS). For each sequence, we evaluated the visibility of the anatomical structures of the central pivot, lateral compartment, and anterior compartment using a semiquantitative score (0=total masking; 1=insufficient visibility; 2=sufficient visibility; 3=optimal visibility). The sum of the scores given to each sequence was divided by the maximal sum, obtaining a percentage visibility index. Friedman and sign tests were used for statistical analysis.

Results

MR examination time was 30–32 min. No patients reported pain, heat or other local discomfort. The visibility index ranged between 83% and 89% for the first four sequences without significant differences among them, 58% for STIR and 11%–36% for the last five sequences. Significant differences were found between each of the four first sequences and the remaining sequences (p<0.004) and between STIR and the last five sequences (p<0.008).

Conclusions

MR imaging of the knee after medial unicompartmental arthroplasty was not associated with adverse events. An imaging protocol including SE, TSE and STIR sequences could be used to study the knee with unicompartmental arthroplasty.     

迭代重建在膝关节置换术后X线数字化断层融合检查中的应用价值

目的：探讨 X 线数字化断层融合（DTS）运用迭代重建技术（IR）,降低膝关节图像金属植入物伪影的可行性和临床应用价值。方法：79例人工膝关节置换术后患者行 DTS 扫描,分别采用滤波反投影重建（FBP）技术和迭代重建（IR）技术对原始图像进行重建。从图像清晰度、假体金属植入物与周围骨相连结构的显示度、金属伪影的多少等方面对两组图像进行分析并评价。根据骨科临床对人工膝关节的分区,在后处理工作站上测量 A1～A7区域内假体与骨之间硬化束金属伪影的长度。结果：对两种重建技术所得到的图像进行主观评价,IR 组优片率为88．6％,FBP 组优片率为62％, IR 组优片率高于 FBP 组,差异有统计学意义（P ＜0．05）。IR 组重建图像在 A1、A3～A7区域无金属伪影,仅3例图像 A2区域见少许金属伪影,A7区域关节间隙内聚氨酸脂软垫显示清晰;FBP 组人工假体在 A1～A7区域均见金属伪影,伪影长度为0．5～2．6 mm。FBP 组图像伪影明显多于 IR 组。结论：有金属植入物的人工膝关节置换术后患者行 DTS 检查,运用 IR 技术可明显减少金属植入物伪影,图像质量明显改善,在术后随访中具有较高的临床应用价值。     

Measurement and comparison of the difference in normal medial and lateral knee joint opening

This paper reports the amount of medial and lateral knee joint opening in the general population. Knee joint lateral and medial opening at 20° knee flexion was quantified on manual varus and valgus stress test, respectively, with custom made device. One hundred men and women between the ages of 20–60 years were evaluated for their joint openings. Patients with previous knee surgeries or chronic knee pains were excluded from the study. Measurements were done twice by two different orthopedic surgeons who were blinded from each other. The mean age of the study group was 39 years (range 20–60 years) and 43 years for women (range 20–60 years) and 34 years for men (range 20–60). The mean lateral and medial knee joint space opening was 7.0° (range 3–9°) and 4.1° (range 2–7°), respectively, in the overall population; in the male population, it was 6.7° (range 3–9°) and 3.9° (range 2–7°), respectively, and in the female population, it was 7.2° (range 3–9°) and 4.3° (range 3–7°), respectively. Conversion to displacement in millimetres, the overall mean lateral and medial joint displacement was 9.3 mm (range 5.1–13.6 mm) and 4.8 mm (range 3.5–10.7 mm), respectively; for males, it was 9.1 (range 5.1–11.9 mm) and 4.6 mm (range 3.5–7.9 mm), respectively, for females, it was 9.8 mm (range 7.2–13.6 mm) and 4.9 mm (range 3.7–10.7 mm), respectively. The prevalence of the overall population that exceeds 6 mm or more lateral joint space opening was 91% (male 90% and female 92%) and medial joint space was 8% (male 4% and female 12%). Statistically, significant differences were seen between medial and lateral opening in male, female and the overall population (p<0.001). The female population exhibited wider opening in both medial and lateral joint opening than the male population (p<0.05). The interexaminer reliability showed no significant difference (p>0.05). More than 91% of the Korean population showed wide lateral joint space opening in the bilateral knee. However, none complained of functional instability or symptoms except for non-pathologic laxity detected by the physician. We strongly recommend bilateral comparison of the knee that has wide lateral joint opening.     

Spontaneous osteonecrosis of the knee involving both the medial femoral condyle and the medial tibial plateau: report of three cases

Spontaneous osteonecrosis of the knee (SPONK) usually involves a single condyle or plateau. The medial femoral condyle (MFC) is most often involved and spontaneous osteonecrosis of the medial tibial plateau (MTP) is a rare condition, representing only 2% of all necroses reported in the knee. SPONK involving both the MFC and the MTP is extremely rare. SPONK occurring in either the MFC or the MTP individually might extend to the corresponding side of the knee in the advanced end-stage; however, in that situation, significant degenerative changes would exist and it might be difficult to differentiate end-stage SPONK form severe osteoarthritis. SPONK affecting both the MFC and the MTP without significant secondary osteoarthritic changes has not been reported, even though it is difficult to know which occurs first. We have cared for three patients with histologically proven osteonecrosis of the MFC and MTP and report their radiologic features.