We found that adipose stem cells are poorly differentiated into bone and that their ability to differentiate into bone varies from cell line to cell line. The osteogenic differentiation ability of the adipose stem cell lines was distinguished through Alzarin Red Staining, and the cell lines that performed well and those that did not were subjected to RNA-seq analysis. The selected gene GSTT1 (glutathione S-transferase theta-1) gene is a member of a protein superfamily that catalyzes the conjugation of reduced glutathione to a variety of hydrophilic and hydrophobic compounds. The purpose of this study is to treat avascular necrosis and bone defect by improving bone regeneration with adipose stem cells introduced with a new GSTT1 gene related to osteogenic differentiation of adipose stem cells. In addition, the GSTT1 gene has the potential as a genetic marker that can select a specific cell line in the development of an adipose stem cell bone regeneration drug.

Total RNA was extracted from each sample using the TRIzol reagent. Its concentration and purity were determined based on A260 and A260/A280, respectively, using a spectrophotometer. RNA sequencing library of each sample was prepared using a TruSeq RNA Library Prep Kit. RNA-seq experiments were performed for hADSCs. Cells were transfected with either GSTT1 at 100 nM or siControl (scramble control) by electroporation using a 1050 pulse voltage for 30 ms with 2 pulses using a 10 μl pipette tip.

The purpose of this study is to discover genetic markers that can promote osteogenic differentiation of adipose stem cells (hADSCs) through mRNA-seq gene analysis. The selected GSTT1 gene was found to be associated with the enhancement of osteogenic differentiation of adipose stem cells. siRNA against GSTT1 reduced osteogenic differentiation of hADSCs, whereas GSTT1 overexpression enhanced osteogenic differentiation of hADSCs under osteogenic conditions.

In this study, GSTT1 transgenic adipose stem cells could be used in regenerative medicine to improve bone differentiation. In addition, the GSTT1 gene has important significance as a marker for selecting adipose stem cells with potential for bone differentiation in the development of a therapeutic agent for bone regeneration cells.

Aims

Taper corrosion has been widely reported to be problematic for modular total hip arthroplasty implants. A simple and systematic method to evaluate taper damage with sufficient resolution is needed. We introduce a semiquantitative grading system for modular femoral tapers to characterize taper corrosion damage.

Aims

This study aimed to evaluate the incidence and prognosis of patients with spinal metastasis as the initial manifestation of malignancy (SM-IMM).

Introduction

In 2010, a widely used metal-on-metal hip implant was voluntarily recalled from the market by the manufacturer. Our lab performed detailed retrieval analysis of 548 of the explanted devices and 165 periprosthetic tissue specimens. We reported a high degree of variability in the multiple measurements that we performed on the components, including volumetric wear.

Other studies using semi-quantitative tissue grading methods to describe the histology of the periprosthetic tissues from metal-on-metal hips have looked for relationships between component wear and histological features. Grammatopoulos et al found higher ALVAL scores in 45 hip resurfacing patients with pseudotumors compared to 11 without pseudotumors and a moderately positive correlation between wear and the histological rankings for tissue necrosis and lymphocytic response.

We examined correlations between the component wear measurements from retrieval analysis and the tissue features in this large group of one metal-on-metal hip design.

Introduction

Embolism in total arthroplasty or hip fractures, coagulation disorders, such as a variety of ways for the prevention of complications of anticoagulation therapy with medication is being done well. The purpose of this study, a representative of the anticoagulation therapy with enoxaparin and drug rivaroxaban of coagulation tests performed in patients between the two groups was to determine whether statistically significant differences.

Introduction

Recently, the combination of press-fit acetabular cup with ceramic articulation is a widely used for implanting cementless acetabular components and has been shown to provide good initial stability. However, these methods may lead to elevating stresses, changing in the bearing geometries, and increasing wear due to deformation of the cup and insert. In addition, there is a potential for failure of ceramic inserts when a large ball head was used because it should be assembled with shallow thickness of the acetabular cup. For risk reduction of it, we applied direct metal tooling (DMT) based on 3D printing for porous coating on the cup. Due to its capability of mechanical strength, DMT coated cup could be feasible to provide better stability than conventional coating. Therefore, we constructed laboratory models for deformation test simulating an press-fit situation with large ceramic ball head to evaluate stability of the DMT coated cup compared with conventional coated cup.

Aims

Children treated for osteosarcoma around the knee often have a substantial leg-length discrepancy at skeletal maturity. The aim of this study was to investigate the results of staged skeletal reconstruction after a leg lengthening procedure using an external fixator in these patients.

Introduction

The purpose of this study was to demonstrate postoperative improvement and high satisfaction rates after a surgical approach that includes arthroscopic labral repair only, in patients with borderline dysplasia, without instability.

Recently, a special type of surface pitting found on metal implants was proposed to arise from “inflammatory cell-induced” corrosion (ICI, Figure 1) (1, 2). The actual mechanism of this was unknown, but similar features were suggested to be artefacts of electrocautery damage from revision surgery (3). Under lab conditions and without the influence of any cells, we aimed to reproduce the same surface pits and structures with electrocautery.

Objectives

We investigated the effects on fracture healing of two up-regulators of inducible nitric oxide synthase (iNOS) in a rat model of an open femoral osteotomy: tadalafil, a phosphodiesterase inhibitor, and the recently reported nutraceutical, COMB-4 (consisting of L-citrulline, Paullinia cupana, ginger and muira puama), given orally for either 14 or 42 days.

Structural bone allografts are a viable option in reconstructing massive bone defects in patients following musculoskeletal (MSK) tumour resection and revision hip/knee replacements. To decrease infection risk, bone allografts are often sterilised with gamma-irradiation, which consequently degrades the bone collagen connectivity and makes the bone brittle. Clinically, irradiated bone allografts fracture at rates twice that of fresh non-irradiated allografts. Our lab has developed a method that protects the bone collagen connectivity through ribose pre-treatment while still undergoing gamma-irradiation. Biomechanical testing of bone pretreated with our method provided 60–70% protection of toughness and 100% protection of strength otherwise lost with conventional irradiation. This study aimed to determine if the ribose-treated bone allografts are biocompatible with host bone.

The New Zealand White rabbit (NZWr) radius segmental defect model was used, in which 15-mm critically-sized defects were created. Bone allografts were first harvested from the radial diaphysis of donor female NZWr, and treated to create 3 graft types: C=untreated controls, I=conventionally-irradiated (33 kGy), R=our ribose pretreated + irradiation method. Recipient female NZWr (n=24) were then evenly randomised into the 3 graft groups. Allografts were surgically fixed with a 0.8-mm Kirschner wire. Post-operative X-rays were taken at 2, 6, and 12 weeks, with bony healing assessed by a blinded MSK radiologist using an established radiographic scoring system. The reconstructed radii were retrieved at 12 weeks and analysed using bone histomorphometry and microCT. Kruskal-Wallis and Mann-Whitney tests were utilised to compare groups, with statistical significance when p<0.05.

Radiographic analysis revealed no differences in periosteal reaction and degree of osteotomy site union between the groups at any time point. Less cortical remodeling was observed in R and I grafts compared to untreated controls at 6 weeks (p=0.004), but was no longer evident by 12 weeks. Radiographic union was achieved in all groups by 12 weeks. Histologic and microCT analysis further confirmed union at the graft-host bone interface, with the presence of mineralising callus and osteoid. Histomorphometry also showed the bridging external callus originated from host bone periosteum and a distinct cement line between allograft and host bone was present at the union site.

Previous studies have shown that the presence of non-enzymatic glycation end products in bone can impair fracture healing. However, these studies investigated bony healing in the setting of diabetic states. Our findings showed that under normal conditions, ribose pretreated grafts healed at rates similar to controls via mechanisms also seen in retrieved human allografts clinically in use. These findings that grafts pretreated with our method are biocompatible with host bone in the rabbit help to further advance this technology for clinical trials.

Aims

Our aim was to investigate the predictive factors for the development of a rebound phenomenon after temporary hemiepiphysiodesis in children with genu valgum.

Aims

The purpose of this study was to investigate the prevalence of sarcopenia and to examine its impact on patients with degenerative lumbar spinal stenosis (DLSS).

Introduction

Most surgeons that have performed kinematically aligned TKA have noticed an overall better clinical outcome, better motion, better patient satisfaction, and a quicker recovery than their patients treated with mechanically aligned TKA.

Introduction

As the proximal femoral bone is generally compromised in failed total hip arthroplasty, achievement of solid fixation with a new component can be technically demanding. Clinical studies have demonstrated good medium-term results after revision total hip arthroplasty using modular fluted and tapered distal fixation stems, but, to our knowledge, long-term outcomes have been rarely reported in the literature. The purpose of this study was to report the minimum ten-year results of revision total hip arthroplasty using a modular fluted and tapered distal fixation stem.

Purpose

The purpose of the present study was to compare functional outcomes of medial unicompartmental knee arthroplasty (UKA) in patients with lateral meniscal lesion (LM (+) group) in the preoperative MRI and those without lateral meniscal pathology (LM (−) group) and to evaluate the effect of lateral meniscus lesion in preoperative MR on functional outcomes after UKA.

Introduction

Patients with osteonecrosis of the femoral head are typically younger, more active, and often require high rates of revision following primary total hip arthroplasty. However, outcomes of revision hip arthroplasty in this patient population have been rarely reported in the literature. The purpose of this study was to report the intermediate-term clinical and radiographic outcomes of revision hip arthroplasty in patients with osteonecrosis of the femoral head.

Introduction

Cementless arthroplasty has been widely used for younger patients with osteoarthritis and other joint pathology. Cementless arthroplasty will be required to porous surface which is to similar to the trabecular bone for bone ingrowth. Titanium Plasma Spray (TPS) has been worldwide used for the porous coating method on arthroplasty. However, TPS coating is limited that would not to establish optimal porosity for bone ingrowth due to arbitary position of melted powder by plasma gas on substrate. Therefore, it is reported coating detached from its substrate (i.e. arthroplasty) is induced implant loosening. Thus, a novel Laser-aided Direct Metal Tooling (DMT) based on Additive Manufacturing (AM) was developed to overcome these limitations. In this study, we were done to assess stereological analysis, static tensile, shear, abrasion test, and physical analysis for evaluation of the efficacy of DMT which was newly-developed coating technology. Then, mechanical characteristics of DMT coating were compared to commercial TPS coating's.

Purpose

The purpose of this study was to demonstrate postoperative improvement and high satisfaction rates after a surgical approach that includes arthroscopic labral repair only, in patients with borderline dysplasia, without instability.

Introduction

Modern ceramic-on-ceramic bearings have become attractive alternatives to conventional polyethylene due to their low wear and minimal particle production. However, ceramic-on-ceramic implants have been associated with ceramic fracture and squeaking. To address these issues, large ceramic heads with a titanium-alloy sleeve have been introduced although limited data are available on their clinical outcomes. The purpose of this study was to report the midterm results of primary total hip arthroplasty using a 32mm with a titanium-alloy sleeve.

Introduction

Highly cross-linked polyethylene has been introduced to decrease osteolysis secondary to polyethylene wear debris generation, but there are few long-term data on revision total hip arthroplasty using highly cross-linked polyethylene liners. The purpose of this study was to report the long-term radiographic and clinical outcomes of a highly cross-linked polyethylene liner in revision total hip arthroplasty.

Purpose

The purpose of this study was to evaluate the postoperative maximal flexion of Robotic assisted TKA which does not increase the posterior condylar offset after surgery and compare CT and conventional radiography in measuring the posterior condylar offset changes.

A small proportion of children with Gartland type III supracondylar humeral fracture (SCHF) experience troubling limited or delayed recovery after operative treatment. We hypothesised that the fracture level relative to the isthmus of the humerus would affect the outcome.

We retrospectively reviewed 230 children who underwent closed reduction and percutaneous pinning (CRPP) for their Gartland type III SCHFs between March 2003 and December 2012. There were 144 boys and 86 girls, with the mean age of six years (1.1 to 15.2). The clinico-radiological characteristics and surgical outcomes (recovery of the elbow range of movement, post-operative angulation, and the final Flynn grade) were recorded. Multivariate analysis was employed to identify prognostic factors that influenced outcome, including fracture level. Multivariate analysis revealed that a fracture below the humeral isthmus was significantly associated with poor prognosis in terms of the range of elbow movement (p < 0.001), angulation (p = 0.001) and Flynn grade (p = 0.003). Age over ten years was also a poor prognostic factor for recovery of the range of elbow movement (p = 0.027).

This is the first study demonstrating a subclassification system of Gartland III fractures with prognostic significance. This will guide surgeons in peri-operative planning and counselling as well as directing future research aimed at improving outcomes.

Cite this article: Bone Joint J 2015;97-B:134–40.

We analysed retrospectively the risk factors leading to femoral overgrowth after flexible intramedullary nailing in 43 children (mean age 7.1 years (3.6 to 12.0)) with fractures of the shaft of the femur. We reviewed their demographic data, mechanism of injury, associated injuries, the type and location of the fractures, the nail–canal diameter (NCD) ratios and femoral overgrowth at a mean follow-up of 40.7 months (25.2 to 92.7). At that time, the children were divided into two groups, those with femoral overgrowth of < 1 cm (Group 1), and those with overgrowth of ≥ 1 cm (Group 2). The mean femoral overgrowth of all patients was 0.6 cm at final follow-up. Overgrowth of ≥ 1 cm was noted in 11 children (25.6%). The NCD ratio was significantly lower in Group 2 than in Group 1, with an odds ratio of 30.0 (p = 0.003).

We believe that a low NCD ratio is an indicator of an unstable configuration with flexible intramedullary nailing, and have identified an association between a low NCD ratio and femoral overgrowth resulting in leg-length discrepancy after flexible intramedullary nailing in paediatric femoral shaft fractures.

Cite this article: Bone Joint J 2013;95-B:254–8.

We examined the differences in post-operative functional disability and patient satisfaction between 56 patients who underwent a lumbar fusion at three or more levels for degenerative disease (group I) and 69 patients, matched by age and gender, who had undergone a one or two level fusion (group II). Their mean age was 66 years (49 to 84) and the mean follow-up was 43 months (24 to 65).

The mean pre-operative Oswestry Disability Index (ODI) and visual analogue scale (VAS) for back and leg pain, and the mean post-operative VAS were similar in both groups (p >  0.05), but post-operatively the improvement in ODI was significantly less in group I (40.6%) than in group II (49.5%) (p < 0.001). Of the ten ODI items, patients in group I showed significant problems with lifting, sitting, standing, and travelling (p < 0.05). The most significant differences in the post-operative ODI were observed between patients who had undergone fusion at four or more levels and those who had undergone fusion at less than four levels (p = 0.005). The proportion of patients who were satisfied with their operations was similar in groups I and II (72.7% and 77.0%, respectively) (p = 0.668). The mean number of fused levels was associated with the post-operative ODI (r = 0.266, p = 0.003), but not with the post-operative VAS or satisfaction grade (p > 0.05). Post-operative functional disability was more severe in those with a long-level lumbar fusion, particularly at four or more levels, but patient satisfaction remained similar for those with both long- and short-level fusions.

Background: The purpose of this study was to evaluate the results after hallux valgus surgery by transar-ticular adductor tenotomy, distal Chevron metatarsal osteotomy and Akin phalangeal osteotomy using medial one incision.

Materials and Methods: From June 2004 to June 2007, eighty feet of 54 patients were included in this study. During the same period, other cases of hallux valgus correction were excluded. Thirty seven patients underwent both feet operation at the same time and 17 patients underwent single foot operation. Among the 37 patients who underwent both feet operation, proximal metatarsal osteotomy was performed for contralateral 11 feet at same time, and these cases with proximal metatarsal osteotomy were excluded from this study. Postoperatively, all patients were allowed immediate full weight bearing walking. Patients were evaluated according to the American Orthopedic Foot and Ankle Society(AOFAS) hallux metatarsophalangeal-interpha-langeal scale, VAS(visual analogue scale), post-operative complications and radiologic parameters such as hallux valgus angle, intermetatarsal angle, T-test was used to evaluate the degree of hallux valgus and intermetatarsal angles. The mean follow up period was 25.9 months.

Results: At the last follow up, the mean AOFAS hallux metatarsophalangeal-interphalangeal scale increased from 48.7 to 91.9. The Mean VAS score decreased from 7.1 to 0.8 post-operatively. The mean hallux valgus angle of 31.4° (range, 22° to 46°) improved to 5.3 ° (range, 0° to 20°) after the operation. The mean intermetatarsal angle also showed improvement from 12.3° (range, 7° to 16°) to 5.5 ° (range, 2° to 11°). Comparison between preoperative and postoperative hallux valgus and intermetatarsal angles was done by T test in dependent groups, which showed statistical significance (p< 0.05). There were three cases of mild hallux varus and three cases of recurred valgus deormity. No avascular necrosis or union problem was observed on the radiographs in any of the patients.

Conclusion: Hallux valgus deformity correction by transarticular adductor tenotomy, distal Chevron metatarsal osteotomy and Akin phalangeal osteotomy using medial one incision has the advantages of lower morbidity and less scar without avascular necrosis of the metatarsal head.

Hip resurfacing has many advantages such as proximal bone conservation and easy revision including conversion to total hip arthroplasty. The major complication in the hip resurfacing is notching at the lateral cortical bone and fracture of the neck. In this research, we simulated the range of direction of reaming without causing notch.

One left femur model was used for the simulation. The femoral head was fitted by a sphere and the origin of Cartesian coordinate was set at the center of the sphere. The simulation was made by imposing a cylindrical cut to the femoral head in varying direction and location. The existence of notching was decided comparing the maximum distance from reaming axis to neck section contour and the radius of cylindrical cut. If the maximum distance is bigger than the radius of cut, the notching exists and vice versa. We simulated existence of notching by varying inclination(α) from 20 to 70 degrees, anteversion(β) from 0 to 30 degree and depth passing through the head center(d) from 0 to 5mm. The implant used for the simulation was Durom^®, Zimmer^©. We selected the implant size that is close to the fitted sphere of femoral head.

No notching was made for any direction when the depth d was less than 2mm. When the depth was 3mm, notching did not generate in the range of α from 43 degrees to 60 degrees and β from 0 to 25 degrees. When the range of depth was from 4mm to 5mm, notching did not generate in ranges of α from 41 degrees to 60 degrees and β from 0 to 29 degrees. The no-notching angle range had tendency increasing slightly when the depth was increased. The angle between the stem of the implant and the neck shaft axis without notching can be calculated from the angle α. When the depth was from 4mm to 5mm, the corresponding angle between stem of implant and the shaft axis was from 120 degrees to 139 degrees.

We hypothesized that navigation can help provide a well-balanced knee, through real-time feedback of alignment accuracies and gap sizes in flexion and extension. The purpose of this study was to evaluate in vivo stabilities of mediolateral laxity in full extension and anteroposterior laxities in 90° of flexion after navigation-assisted total knee arthroplasty, and to determine the nature of the correlations between these and range of motion (ROM).

Forty-two total knee arthroplasties performed using a navigation system with a minimum two-year follow-up were included. The following were measured at final follow-ups; mediolateral laxities at extension and anteroposterior laxities at 90 degrees of flexion (using stress radiographs and a Telos arthrometer), modified HSS scores (excluding laxity and range of motion), and range of motion (ROM).

At final follow-up the mean modified HSS score was 82% of total points and mean postoperative ROM was 128.1 ± 10.4°. Mean medial laxity was 3.5 ± 1.4°, mean lateral laxity 4.4 ± 2.2°, and mean anteroposterior laxity 7.1 ± 4.1 mm. We found no significant correlation between mediolateral laxity and postoperative ROM. However, a significant correlation was found between postoperative ROM and anteroposterior laxity.

In the present study, the use of a navigation system in total knee arthroplasty was found to improve in vivo stability and produce promising short-term clinical results.

Summary: Using a navigation system in total knee arthroplasty, we obtained good in vivo stability and found the positive correlation between the range of motion and anteroposterior laxity

A consecutive series of patients who underwent 113 total hip arthroplasty (THA) with minimally invasive surgery (MIS) (63 one-, 50 two-incision cases) were studied. One-incision THA was performed with a posterolateral approach. For the two-incision, the first incision for cup insertion was made over the anterolateral side of the hip and intermuscular dissection was performed between the gluteus medius and the tensor fascia lata. The second incision for stem insertion was made on the posterolateral side along the fiber of the gluteus maximus and intermuscular dissection was made between the gluteus medius and the piriformis.

The average length of the skin incision and standard deviation (SD) in the one- and two-incision group was 7.5 ± 0.54 cm and 12.1 ± 0.93 cm (p < 0.001). Average surgical time for the two groups (and SD) was 52 ± 8.5 minutes and 70 ± 10.2 minutes (p = 0.042) in the one and two incision groups respectively. Fluoroscopy was used in the two-incision group for an average 6.0 ± 5.3 seconds. In the one-incision group, the average time was 1.3 ± 2.1 seconds.

The patients in the one-incision group could walk on crutches at postoperative 3.7 days on average, and in the two-incision group at 1.6 days on average (p = 0.000). In the one-incision group, patients used crutches for 6 weeks on average, and in the two-incision group, patients used crutches for 3 weeks on average (p = 0.042).

Complications that developed within 1 month of surgery in the one-incision group were: 1 case of DVT, 1 case of intra-operative fracture and 1 case of dislocation; for the two incision group there were: 1 case of DVT, 1 case of intra-operative fracture and 1 case of femoral nerve entrapment.

Before surgery, the HHS for the one-incision group was 49.8 points, and for the two-incision group it was 49.6 points (p > 0.05). At the time of the follow up review conducted postoperatively 1 year, the average HHS was not significantly different (p > 0.05). However, the average function score in HSS for the two-incision group was superior to that of the one-incision group (p = 0.045). Preoperative WOMAC scores were not different for the two groups (68.7 in one-incision group and 70.9 in two-incision group, respectively, p > 0.05). However, the average WOMAC score for the two-incision group was better, especially for the function score (p = 0.001). The other hip functions, common in oriental persons, were also better in the two-incision group compared to the one-incision group.

On the radiographs, the location of the femoral prosthesis inserted in the medullary cavity was usually central in both groups; only 4 cases showed varus in the one-incision group and 2 cases in the two-incision group. The opening angle of the acetabular component was 38.1° in the one-incision group and 39.2° in the two-incision group (p > 0.05). The anteversion of the acetabular component was 21.0° in the one-incision group and 22.2° in two-incision group (p > 0.05).

As compared with one-incision MIS-THA, two-incision MIS-THA, although it is a more difficult procedure, produces superior results, recovery was faster and patient satisfaction was higher due to early rehabilitation and reduced soft tissue damage without increasing the complication frequency.

Typical navigation system to insert hip implants in the accurate position consists of a 3D position measurement device and a computer. These navigation systems are classified into two categories according to the method of identifying the anterior pelvic plane that works as the reference of the orientation of the acetabulum cup. The preparation process for imageless navigation system is very easy because it uses three anatomical bony markers to define the anterior pelvic plane. When these anatomical bony markers are hard to locate, especially at the pubic symphysis due to the thick soft tissue, the accurate direction of the cup cannot be secured. The aim of this study is to estimate the soft tissue thickness without using the patient’s specific data such as the A-mode ultrasound image or C-arm image.

In our previous study, it was pointed out that the thickness of the hypodermic fat obtained through an ultrasound image could be estimated using the patient’s BMI and the displacement created by a specific force. Considering the probe shape, the soft-tissue thickness estimation formula is expressed as follows:

\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[Y_{estimated_thickness}\ =\ k(b_{0}\ +\ b_{1}\ {\times}\ BMI\ +\ b_{2}{\times}\ {\delta})\] \end{document}

k: constant for the shape of the probe end

Only two kinds of the probe end shapes (flat-ended probe and spherical-ended probe) were considered, and the change in the k value corresponding to the radius was calculated using the FE model of the soft tissue for each subject. The finite-element model was constructed as axisymmetric.

The simulation result of the initially assumed variables and the measured result were compared, and the optimization method was used to minimize the error: The RMS difference between the result of the experiment and that of the analysis was taken as the objective function. With the FE analysis for the two kinds of probe shapes with one subject, we determined the shape variable (k).

From the formula composed by a model with data from 28 people, the average error was 3 mm equivalent to the angle error of less than 1°. Therefore, the use of the method suggested in this study will help to improve the acetabulum cup navigation in THA, when we use only the surface points on the soft tissue. In addition, it seems that the soft-tissue thickness estimation formula suggested in this study may be generally used.

Background: There area some controversies about the need for revision of well fixed femoral stem during the revision total hip arthroplasty. The purpose of this study is to evaluate the state of unretrieved femoral stem, in revision total hip arthroplasty where only acetabular component was revised.

Methods: From January 1998 to December 2004, thirty-one patients underwent revision total hip arthroplasty whose well fixed femoral stem was retained and acetabular components revised. Twenty-six patients(29hips) with a minimum follow-up of three years were included in this study. Out of those twenty-six patients, sixteen patients(18hips) were male and ten patients(11hips) were female with an average age of 54.3 years for the study group. The average time from the primary operation until the revision surgery was 9.2 years and the average follow-up period after the revision was 5 years. The femoral head component was exchanged in all cases and same size femoral head component was used in eleven hips. The clinical results wee analyzed using Harris Hip Score, and the radiographs were reviewed for stability of acetabular components, femoral stem, and degree of osteolysis and radiolucent lines.

Results: The average Harris Hip score improved from 56.3 points preoperatively to 89.8 points postoperatively. Femoral stems were found to be stable in all hips. Sixteen hips(55.2%) showed evidence of osteolysis and seven hips(24.1%) showed non-progressive radiolucent lines. The osteolysis was detected at Gruen Zone I and VII in most of the affected hips except for two hips which showed distal osteolysis. The average life of femoral stem from primary operation until the final follow up varied from 10.8 years to 18.2 years, with the average being 14.2 years.

Conclusions: We recommended that well fixed, stable femoral components can be retained at the time of revision total hip arthroplasty.

Level of evidence: Therapeutic Level IV

Many reports show good results following procedures, such as intervertebral body fusion using cage or total disc replacement, that restore adequate disc height. However, there have been no references regarding the range of normal lumbar disc height in Korean adults which can be used as a standard for the implant size. The purpose of our study is to measure the lumbar disc height on radiographs in normal Korean. 132 subjects (age range 20 to 40 years) who had no previous history of low back pain and no significant finding on physical examination were enrolled. Plain lateral lumbar spine radiograph in supine position were taken. Intervertebral disc heights were measured at anterior, middle and posterior portion of each lumbar disc. The average magnification rate was 115%, and the disc heights were corrected by the magnification rate in each segment.

Lumbar disc height showed cranio-caudal pattern in both male and female groups. L4–5 disc heights were highest at anterior, middle and posterior portion in male. L4–5 disc heights were highest at middle and posterior portion in female. L5-S1 disc height was highest at anterior portion in female, but there was no statistically significant difference between L4–5 and L5-S1 disc height at anterior portion. There was no significant difference in disc height between male and female except anterior portion of L1–2 and L2–3 disc. Statistically significant decrease in disc height was not presented in overweight person at all measured site in male and female except posterior portion of L1–2 disc in male.

This research is meaningful in that it is an attempt to provide a reference value of lumbar disc height in Korean adults, and the measured values may also be useful in manufacturing Korean modeled artificial lumbar disc prosthesis or surgical instruments for lumbar interbody fusion.

Recently with the introduction of operations using various instrument of total ankle arthroplasty, we are showing quite satisfactory short term results on the treatment of resolved pain of ankle joint. However, there have been reports of high probability of complication from total ankle arthroplasty to other arthroplasty applied to other joints. Therefore in order to make the results of ankle arthroplasty superior, it is necessary to reduce these complications. We try to analyze complications that occur often and come up with the best results.

There were 45 cases of 42 patients of HINTEGRA^® (Newdeal SA, Lyon, France) model from November 2004 to August 2006. Follow up averaged 33.5 months, the average age of patients was 61.1 years, with 14 males and 28 females. We evaluated the complications and analyzed the causes of failures. There was a total 15 cases of complications; 5 cases of medical impingement syndrome, 3 cases of varus malposition, 2 cases of delayed healing of wound, 1 case of peroneal nerve problem, medial malleolar fracture, postoperative deep infection and gouty arthritis pain and Achilles tendinitis.

Our conclusion is that total ankle arthroplasty had more complication rate than other joint arthroplasty, so we need a more meticulous preoperative and perioperative care.

We reviewed the results of a selective à la carte soft-tissue release operation for recurrent or residual deformity after initial conservative treatment for idiopathic clubfoot by the Ponseti method. Recurrent or residual deformity occurred in 13 (19 feet) of 33 patients (48 feet; 40%). The mean age at surgery was 2.3 years (1.3 to 4) and the mean follow-up was 3.6 years (2 to 5.3). The mean Pirani score had improved from 2.8 to 1.1 points, and the clinical and radiological results were satisfactory in all patients. However, six of the 13 patients (9 of 19 feet) had required further surgery in the form of tibial derotation osteotomy, split anterior tibialis tendon transfer, split posterior tibialis transfer or a combination of these for recurrent deformity.

We concluded that selective soft-tissue release can provide satisfactory early results after failure of initial treatment of clubfoot by the Ponseti method, but long-term follow-up to skeletal maturity will be necessary.

Only limited data exists concerning outcomes after total knee arthroplasty (TKA) using a surgical robot. We conducted this study to evaluate the clinical and radiographical results in robotic-assisted implantation of TKAs with a minimum follow-up of two years.

A total of 50 primary TKAs using ROBODOC were included in this study. The mean duration of follow-up was 28.3 months. The radiographic measurement with regard to the change of mechanical axis, and the inclination of the femoral and tibial components were assessed. The value within ± 3° of optimum was classified to be “acceptable”, and the value exceeding more than ± 3° to be “outlier” results. Also we evaluated clinical results with the range of motion (ROM), Hospital for Special Surgery (HSS) scores, and Western Ontario and McMaster University (WOMAC) scores.

The mechanical axis was changed from 6.57 varus to 0.81 valgus. Mean coronal inclination of the femoral and tibial component were 88.61 and 89.76 at the last follow up. Also, mean sagittal inclination of the femoral and tibial component were 0.82 and 85.49. On the other hand, all prostheses had no radiolucent lines. On the clinical assessment, the range of motion improved from 124.9 to 128.4, and the improvement of HSS score and Womac score were 70.06 to 95.72 and 65.64 to 28.92 in each. No major adverse events related to the use of the robotic system have been observed. However, one case of the formation of seroma around the pin track and two cases of the partial abrasion of patellar tendon occurred in relation to procedures.

A surgical robot system in TKAs provides good clinical and radiographical results at least 2 years follow-up, however further study for the long term follow-up may be needed. A clear advantage of robot-assisted TKA seems to be ability to execute a highly precise preoperative planning and intraoperaive procedures. But current disadvantages such as increased operating times and inability of adjusting the preoperative planning during the procedure have to be resolved in the future.

Navigation was used to achieve a balanced flexion-extension gap for total knee arthroplasty and it’s 3 years clinical results were reported.

From 112 osteoarthritic knees with varus deformity the flexion and extension gap were measured with distraction of 50 lb/inch using special torque wrench following completion of controlled medial release with guidance of navigation system & tibial bone cut. Distal & AP femoral bony cut were finished according to the data of measurement of flexion-extension gap. After confirmation of the balanced flexion-extension gap by navigation total knee arthroplasty was completed.

The differences between flexion and extension gap varied from case to case, and could be classified into 3 kinds; balanced, tight flexion gap and tight extension gap.

HSS score was 96.7, ROM was 128.5 degree. 39 patients (35%) can have comfortable kneeling 75 patients(67%) can sit with cross leg. Gap technique with navigation could provide excellent clinical results of total knee arthroplasty and 3 classifications of flexion and extension gap should be taken into considerations for balanced total knee arthroplasty

Long term successful results of high tibial osteotomy (HTO) strongly depend on the degree of correction, and inadequate intraoperative measurements of the leg axis can lead to under or over correction, and surgeons have to solve these problems based on personal experience.

This study was undertaken to investigate and compare the clinical and radiological results of navigation assisted open wedge high tibial osteotomy (HTO) versus conventional HTO at 12 months after surgery, for unicompartmental gonarthrosis.

Forty navigated open HTOs with an anterior opening gap of approximately 70% of the posterior gap were included and compared with forty open HTOs performed using the conventional cable technique in terms of intraoperative leg axis assess.

Navigated HTOs corrected mechanical axes to 2.9° valgus (range 0.5–6.2) with few outliers (12.5%), and maintained posterior slopes (7.9±2.3° preoperatively and 8.3±2.8° postoperatively) (P> 0.05). However, in the conventional group, only 63% of cases were within the satisfactory range (valgus 2–5°), and tendencies toward undercorrection and an increase in posterior slope were observed. Clinically both groups showed satisfactory results.

Navigated HTO significantly improved the accuracy of postoperative mechanical axis and decreased correction variabilities with fewer outliers.

The navigation system recently introduced in an ACL reconstruction is reported that it would be helpful for determining the accurate tunnel position and better clinical results in. It also provides intra-operative information such as knee kinematics and anteroposterior translation and internal-external rotation of the tibia during the reconstruction. Our hypothesis was that a double bundle reconstruction would provide better anteroposterior and rotational stabilities than a single bundle reconstruction.

The aim of this study was to assess the changes of anteroposterior and rotational stabilities using a navigation system achieved by double bundle reconstruction (20 knees) and compare them with those by single bundle reconstruction (20 knees).

After registering the reference points, anteroposterior ad rotational stability test with 30° knee flexion using a navigation system was carried out and measured before and after reconstruction on both groups.

The anteroposterior stability showed significant improvement from 17.5 mm before the reconstruction to 5.1 mm after the reconstruction in the double bundle group and from 16.6 mm to 6.1 mm in the single bundle group, showing a significant inter-group differences (p< .05). The mean rotation stability of the double bundle group showed more significant improvement after reconstruction than those of the single bundle group (9.8° in single and 6.1° in double bundle group, p< .05).

The double bundle ACL reconstruction tends to be more stable in rotational stability than the single bundle reconstruction, but not so much in anteroposterior stability. Clinically the double bundle ACL reconstruction may provide better rotational stability reducing residual pivot shift phenomenon after reconstruction.

Unexpected findings were sometimes observed such as hyper extension, oversize of femoral component, or anterior notching of anterior femoral cortex in total knee arthroplasty (TKA) using computer system. We conducted this study to evaluate these findings by a virtual simulation using ORTHODOC and then confirmed them on real patients with TKA.

Virtual simulations of distal femoral cut in 50 patients using ORTHODOC system were made by way of being perpendicular to mechanical axis (CAOS way) and to intramedullary guide (manual way) in the same knee and measured the difference of sagittal cutting planes. We compared the maximum AP dimensions of femoral condyle parallel to distal cut plane. We also compared sagittal alignment and size of the femoral component in 30 bilateral TKAs, one side using ROBODOC (CAOS way) and the other side using IM guide (manual way).

On virtual simulation, distal femoral cut was more extended (3.1±1.6°) in CAOS than in manual way and anteroposterior size of the femoral condyle in CAOS way was also larger than in manual way (p=0.001). Radiographic sagittal alignment of femoral component performed using CAOS way was slightly more extended than those using manual way, showing a significant difference (p=0.024). The larger femoral components were required in six patients on CAOS and in two patients on manual way, whereas twenty-two patients showed same size on both side.

CAOS can provide more accurate sagittal cut perpendicular to mechanical axis than manual system, which may lead to slightly extended position or larger femoral component.

In total knee arthroplasty, navigation systems that help achieve accurate alignment of the lower limbs have been applied widely, and these techniques are currently being used in minimally invasive unicondylar knee arthroplasty (MIS UKA) with good alignment results. To the best of our knowledge, there are no studies showing whether or not MIS UKA using a navigation system has a significant influence on the clinical results. This prospective study investigated the hypothesis that minimally invasive uni-compartmental knee arthroplasty using navigation system (NA-MIS UKA) will produce better short-term clinical results than MIS UKA without navigation system.

After a minimum two-year follow-up, the short-term functional results included the ranges of motion, Hospital for Special Surgery (HSS) scores, and WOMAC scores and the alignment accuracy of the components of 31 NA-MIS UKAs (NA-MIS group) compared with those of 33 MIS UKAs without a navigation system (MIS group). The surgery time was also recorded and compared.

The HSS and WOMAC scores showed significant improvement at the final follow-up in both groups, showing no significant inter-group difference (p=0.071, p=0.096, respectively). The ranges of motion also showed significant improvements in both groups, but there was no significant difference between two groups (p=.687). However, the surgery time was longer in MIS group than in NA-MIS group. NA-MIS UKA produces significant improvement in the desired mechanical axis with prosthetic alignment outliers compared with that without the navigation system.

However, at the final follow-up, there were no significant differences in any of the functional parameters between the two groups.

This prospective study was undertaken to compare the clinical and radiological results achieved using navigation assisted minimally invasive (NA-MIS) and conventional (CON) techniques in bilateral total knee arthroplasty (TKA).

Forty-two bilateral patients with a minimum 2-year follow-up who were available for study after NA-MIS TKA were included in this study. Clinical evaluations (ROM, HSS and WOMAC scores) were performed at 3 and 6 months and at 1 & 2 year postoperatively. Patient subjective preferences and radiological accuracies were compared at 1 year postoperatively.

Preoperative HSS scores were 68.5 in the NA-MIS group and 66.5 in the CON group, and these scores improved to 93.6 and 92.5 at 1 year postoperatively, respectively. Knees had a higher average HSS score in NA-MIS group than in the CON group till six months, but not after nine months postoperatively. In terms of WOMAC scores, pain scores in the NA-MIS group were better up to nine months postoperatively, but not at one & 2 year postoperatively, and total WOMAC scores were better up to six months, but not after nine months postoperatively. ROM was comparable in both groups at all times. However, more patients preferred NA-MIS sides than CON sides. Radiological results demonstrated no difference between the mean values of the two groups, although the NA-MIS group contained fewer outliers than the CON group.

NA-MIS TKA results in better functional scores than CON-TKA over the first or nine months postoperatively. However, no differences in any functional parameters were evident at one & two year postoperatively.

Computer based navigation system improved the accuracy of limb and component alignment and decreased the incidence of outliers. The majority of previous studies were based on the infrared navigation system. We evaluate the availability and accuracy of the electromagnectic(EM) navigation system in total knee arthroplasty

From July 2006 to January 2007, 40 patients (50 TKAs) with osteoarthritis were participated in this study. AxiEM(Medtronics) was used and Nexgen CR(26 cases), and Nexgen CR flex(24 cases) were used. We analyzed the failure mode of navigation (7 cases), operation time and radiologic results (limb and component alignment)

Total registration time was 4 minutes 45 seconds in average (Range : 3 minutes 45 seconds ~ 6 minutes 55 seconds). Failures in clinical applications resulted from non-recognition of EM tracker or paddle by metallic interference in 4 cases and from informational changes during surgery by fixation loss or loosening of the tracker in 3 cases. Radiologically, the mechanical axis changed from −11.2±7.21 (Range : −25.8~3.1) to 1.0±1.25(Range : −2.1~4.0) and 1 case of outlier occurred (valgus 4°). Component alignment is measured as followed: 89.3±1.6° of Theta angle, 89.9±1.5° of Beta angle, 1.8±2.5° of Gamma angle, 86.1±2.9 of Delta angle°. There were no complications related to the EM navigation.

The EM navigation system helped to achieve accurate alignment of component and lower leg axis without any complications. It had several advantages such as relatively less invasiveness in fitting small instruments, not disturbing operation field, no interrupted line of sight, portable use, and applicability to any implant. However, metallic interference may be still problematic.

The EM navigation had advantages; less invasiveness, no disturbing operation field, no interrupted line of sight, portable use and applicability to any implants. But metallic interference may be still problematic.

Correct alignment of the leg and positioning of the implant has shown to be an important factor in the successful long term outcome of total knee arthroplasty and navigation systems enable an accuracy of corrections and alignment within intervals of 1 mm or 1 degree. This study is to test if there is any discrepancy in accuracy which was sometimes observed in clinical trials between Orthopilot (Aesculap, Tuttlingen, German) and AxiEM (Medtronic Navigation, CoalCreek, Colo., USA).

A synthetic bone model (Sawbones, Pacific Laboratories, Vashon, Washington) including pelvis and leg with mobile joint made up of titanium which does not affect the electromagnetic field was constructed. Mechanical axis was checked by ORTHODOC system (Integrated Surgical System, CA, USA) that is a preplanning system for ROBODOC (ISS, CA, USA) assisted total knee arthroplasty (TKA) and total hip arthroplasty (THA). The CT images were scanned with 1.25 mm or less slice interval. The CT images were converted to 3-dimensional (3D) volume-rendered model in ORTHODOC. Two orthopaedic surgeons measured it ten times independently.

For the measurement of mechanical axis using navigation, 4 orthopaedic surgeons (two experts having more than 100 navigation experiences and two residents) registered anatomical landmarks and kinematic center of bone model ten times using Orthopilot as well as AxiEM. After that, one surgeon intentionally registered the wrong anatomical landmarks (10 mm medial and lateral to the center of distal femur, proximal tibial and ankle, and both malleoli) in both navigation system and observed the change of mechanical axis.

True mechanical axis was varus 1.25° using Orthodoc, Orthopilot displayed varus 1.10±0.64° and AxiEM did varus 1.78±0.79°. The difference of mechanical axis between two navigations was not observed (P=0.12) and there were no intra and inter-observer variation in statistical analysis (Correlation=0.934, P=0.00). In the case of erroneous identification of the anatomical landmarks, Orthipilot showed much less variation compared to AxiEM. AxiEM altered the mechanical axis more in palpating center of the distal femur and ankle center and Orthopilot did in palpating the center of ankle.

Both navigation systems provide high accuracy and reproducibility of mechanical axis of lower limb in experimental condition. But both were affected by the wrong identification of the anatomical landmarks. AxiEM had more variations. So surgeon should pay attention to register the precise anatomical landmarks.

Bilateral sequential total knee replacement with a Zimmer NexGen prosthesis (Zimmer, Warsaw, Indiana) was carried out in 30 patients. One knee was replaced using a robotic-assisted implantation (ROBOT side) and the other conventionally manual implantation (CON side). There were 30 women with a mean age of 67.8 years (50 to 80).

Pre-operative and post-operative scores were obtained for all patients using the Knee Society (KSS) and The Hospital for Special Surgery (HSS) systems. Full-length standing anteroposterior radiographs, including the femoral head and ankle, and lateral and skyline patellar views were taken pre- and post-operatively and were assessed for the mechanical axis and the position of the components. The mean follow-up was 2.3 years (2 to 3).

The operating and tourniquet times were longer in the ROBOT side (p < 0.001). There were no significant pre- or post-operative differences between the knee scores of the two groups (p = 0.288 and p = 0.429, respectively). Mean mechanical axes were not significantly different in the two groups (p = 0.815). However, there were more outliers in the CON side (8) than in the ROBOT side (1) (p = 0.013). In the coronal alignment of the femoral component, the CON side (8) had more outliers than the ROBOT side (1) (p = 0.013) and the CON side (3) also had more outliers than the ROBOT side (0) in the sagittal alignment of the femoral component (p = 0.043). In terms of outliers for coronal and sagittal tibial alignment, the CON side (1 and 4) had more outliers than the ROBOT side (0 and 2).

In this series robotic-assisted total knee replacement resulted in more accurate orientation and alignment of the components than that achieved by conventional total knee replacement.

The aim of study was to provide normal value of anteroposterior and rotational stability of knee joints using navigation system.

From March 2007 to November 2007, 35 patients (23 men, 12 women) with a mean age of 36.1(16–57) years, who were treated with arthroscopy, without ligament injury of knee were included in our study. We measured amount of anteroposterior displacement and rotation of the knee in 0, 30, 60 and 90 degrees of flexion position using Orthopilot navigation system. All tests were performed by same single surgeon under manual maximal force.

The mean anterior displacement was 3.7±2.0, 6.6±2.2, 5.8±2.0 and 4.7±1.8 mm in 0, 30, 60 and 90 degrees of flexion respectively. The amount of anterior displacement at 30 degree of flexion was significantly larger than those of other degrees. The mean posterior displacement was 2.0±0.5, 2.2±0.4, 2.1±0.4 and 2.0±0.6 at each degree. There was no statistical difference in posterior displacement. The mean internal rotation was 10.3±2.7, 14.6±3.3, 16.2±2.9 and 15.0±4.3 degree at each degree. The amount of internal rotation at 0 degree of flexion was significantly smaller than those of other degrees. The mean external rotation was 8.4±3.4, 16.5±3.3, 13.3±3.8 and 15.0±4.3 degree at each degree. The amount of external rotation at 0 degree of flexion was significantly smallest and that of 30 degree was largest.

In the measurement of laxity using navigation, we could acquire previously mentioned results. The measurement of stability of knee will be useful in diagnosing ligament injury and evaluating degree of postoperative symptomatic improvement.

We studied 11 patients with checkrein deformities of the hallux who underwent surgical treatment. Six had lengthening of the flexor hallucis longus tendon by Z-plasty in the midfoot, and five underwent release of adhesions and lengthening of the tendon by Z-plasty at the musculotendinous junction at the fracture site.

All six patients who underwent Z-plasty at the midfoot showed complete correction of the deformity without recurrence. Of the five who had release of adhesions and Z-plasty of the tendon at the fracture site, two showed partial and one showed complete recurrence.

In the cementless total hip arthroplasty, the position of the stem is pretty much determined by broach and rasping with which the is required for two reasons: one is to align the stem with the femur at the desired position and the orientation. The other is to achieve the conformity between the stem and the prepared proximal cavity surface in the femur. The robotic hip surgery can be a solution for the accurate of femoral canal shaping, but recent reports about the clinical follow-up study of the robotic hip surgery indicated frequent dislocation mainly due to the excessive soft tissue damage during robotic operation. In this paper, a guide being inserted into the femoral canal is proposed to restrict the undesired motion of the rasp inside the femur without extra incision.

A set of canal guide and custom rasp for the selected stem(versys fibermetal midcoat, zimmer co.)were developed and tested with 4 synthetic femurs (model 1130, Sawbones co.). After rasping, a plastic copy of the stem was inserted into the femur and sliced at 5 mm thickness. From obtained cross sections, percentages of the gap larger than 0.3mm between the stem and the bone was measured. 6_C_Results: In average, 79% of bone-implant interface was close contact. Valgus/varus deviations of the stem were 0.40±0.45 degree, which means the angle of axis of straight reamer and axis of final cut.

In average, 79% of bone-implant interface was close contact. Valgus/varus deviations of the stem were 0.40±0.45 degree, which means the angle of axis of straight reamer and axis of final cut.

The conformity of femoral canal with the femoral stem in this approach was higher than the conventional hip surgery and comparable to those in the robotic surgery. The alignment of the stem within the femur is also as good as those in the robotic surgery(0.34±0.67 approach does require neither expensive system nor CT scan. Also this approach can be executed swiftly without extra time and unnecessary large incision compared with the robotic surgery.

The purpose of this research is to propose CT-free cup orientator using tilt sensors without expensive point tracking devices in total hip replacement. In the case of using a mechanical guide, the accuracy of cup orientation can be sacrificed because of change of the patient’s posture during procedure. Several navigation systems have been introduced to secure an accurate position and orientation of the implant in THR. These systems are expensive and have some weakness due to possible interference inoptical measurement. Our orientator employs a T-bar shaped gauge and economic tilt sensors to secure a fairly orientation of acetabular cup inTHR.

The T-bar gauge having three feet with adjustable distance is designed to obtain the anatomical landmarks concurrently. Each foot is placed on the anatomical landamark of the sawbone. The gauge has its own tilt sensor to identifiy the tilt angle of the guage using AD input board. Similary, the cup positioning tool and dynamic reference base (DRB) have their own tilt sensors. The experimental procedures of CT-free cup orientator are done as follows:

Place the T-bar gauge in right place on the pelvis by setting three feet on the ASIS and pubic.

We define errors as difference between experimental data and ground truth obtained by Micro-Scribe (Immersion Inc.) Errors of the cup in abduction and anteversion were 1.2 and 1.0 degrees respectively when the test is performed on a sawbone.

We analyzed the causes of error to improve the accuracy of our cup orientator. Measuring landmarks and aligning three tilt sensors seemed to cause some errors. Base on this study, we expect to make an experiment on cadaver.

Aims: To simulate intra-articular fracture healing, this study investigated the regeneration of identical osteochondral gaps within step-offs or on congruous articular surfaces. Methods: Twenty-nine rabbits received either half-millimetre coronal step-offs separated by 0.5X2mm osteochondral gaps (n=16) or identical osteochondral defects alone (n=13) on the medial femoral condyles. After 6, 12 and 24 weeks survival, subchondral bone density about the lesion was measured by pQCT. Cartilage regeneration/degeneration was evaluated with histology and immunostaining for collagen type I and II. Results: Subchondral bone re-establishment was complete in gaps within step-offs by 24 weeks however, showed delayed restoration in defects on congruent surfaces. Repair cartilage quality showed some differences in the two groups producing better results on the low side of step-off group. Increased subchondral bone density associated with moderate cartilage degeneration attributable to high contact stresses was observed at the high sides of stepoffs. Neither bone density changes nor cartilage damage was present around defects on congruent surfaces. Collagen type I content showed decreasing while type II increasing trend in repair cartilage with longer follow-ups in both groups. Conclusions: Osteochondral defects at unloaded surface segments of step-offs displayed different, in certain regards slightly superior repair characteristics than those on congruent surfaces. Minor separation of the two sides of the offsets did not result in severe local degeneration.