Lumbar spine segmentation in MR images: a dataset and a public benchmark

This paper presents a large publicly available multi-center lumbar spine magnetic resonance imaging (MRI) dataset with reference segmentations of vertebrae, intervertebral discs (IVDs), and spinal canal. The dataset includes 447 sagittal T1 and T2 MRI series from 218 patients with a history of low back pain and was collected from four different hospitals. An iterative data annotation approach was used by training a segmentation algorithm on a small part of the dataset, enabling semi-automatic segmentation of the remaining images. The algorithm provided an initial segmentation, which was subsequently reviewed, manually corrected, and added to the training data. We provide reference performance values for this baseline algorithm and nnU-Net, which performed comparably. Performance values were computed on a sequestered set of 39 studies with 97 series, which were additionally used to set up a continuous segmentation challenge that allows for a fair comparison of different segmentation algorithms. This study may encourage wider collaboration in the field of spine segmentation and improve the diagnostic value of lumbar spine MRI.

Clinical Utility of An Intervertebral Motion Metric for Deciding on the Addition of Instrumented Fusion in Degenerative Spondylolisthesis

STUDY DESIGN

A prospective single-arm clinical study.

OBJECTIVE

To explore the clinical utility of an intervertebral motion metric by determining the proportion of patients for whom it changed their surgical treatment plan from decompression only to decompression with fusion or vice versa.

SUMMARY OF BACKGROUND DATA

Lumbar spinal stenosis (LSS) from degenerative spondylolisthesis is commonly treated with decompression only or decompression with additional instrumented fusion. An objective diagnostic tool capable of establishing abnormal motion between lumbar vertebrae to guide decision-making between surgical procedures is needed. To this end a metric, based on the vertebral sagittal plane translation-per-degree-of-rotation (TPDR) calculated from flexion-extension radiographs, was developed.

METHODS

First, spine surgeons documented their intended surgical plan. Subsequently, the participants' flexion-extension radiographs were taken. From these the TPDR was calculated and reported as a Sagittal Plane Shear Index (SPSI). The SPSI metric of the spinal level intended to treat was used to decide if the intended surgical plan needed to be changed or not.

RESULTS

SPSI was determined for 75 participants. Of these, 51 (68%) had an intended surgical plan of decompression only and 24 (32%) decompression with fusion. In 63% of participants the SPSI was in support of their intended surgical plan. For 29% of participants the surgeon changed the surgical plan after the SPSI metric became available to them. A suggested change in surgical plan was overruled in 8% of participants. The final surgical plan was decompression only for 59 (79%) and decompression with fusion for 16 (21%) participants.

CONCLUSION

The 29% change in intended surgical plans suggested that SPSI was considered by spine surgeons as an adjunct metric in deciding whether to perform decompression only or or to add instrumented fusion. This change exceeded the a priori defined 15% considered necessary to show potential clinical utility of SPSI.

Controversies around hip fracture treatment: clinical evidence versus trends from national registries

PURPOSE

Several controversies in the optimal treatment of femoral neck fractures persist, together with large variations in clinical practice.

METHODS

A narrative literature review covering 4 current controversies in the surgical management of femoral neck fractures (total hip arthroplasty (THA) versus hemiarthroplasty (HA), cemented versus uncemented HA, internal fixation versus arthroplasty, operative versus non-operative) was performed. Available literature was balanced against annual trends in the management of femoral neck fractures from the public domain of several national registries (Sweden, Norway, The Netherlands, Australia and New Zealand).

RESULTS

For most controversies, the literature provides stronger evidence than is reflected by variations encountered in daily practice. Implementation of clinical evidence tends to lag behind and important differences exist between countries.

CONCLUSIONS

Trends of clinical practice from national registries indicate that implementation of available clinical evidence needs to be improved.

No difference in bacterial contamination of hip capsule sutures and control sutures in hip arthroplasty surgery

BACKGROUND

Perioperative preventive measures are important to further reduce the rate of periprosthetic joint infections (PJI) in patients undergoing total hip arthroplasty (THA). During THA surgery, joint capsule sutures are commonly placed to optimize exposure and reinsertion of the capsule. Bacterial contamination of these sutures during the procedure poses a potential risk for postoperative infection. In this exploratory study, we assessed the contamination rate of capsule sutures compared to the contamination of the remains of exchanged control sutures at the time of closure.

METHODS

In 100 consecutive patients undergoing primary THA capsule sutures were exchanged by sterile sutures at the time of capsule closure. Both the original sutures and the remainder of the newly placed (control) sutures were retrieved, collected and cultured for ten days. Types of bacterial growth and contamination rates of both sutures were assessed.

RESULTS

Sutures from 98 patients were successfully collected and analyzed. Bacterial growth was observed in 7/98 (7.1%) of the capsule sutures versus 6/98 (6.1%) of the control sutures, with a difference of 1% [CI -6-8]. There was no clear pattern in differences in subtypes of bacteria between groups.

CONCLUSIONS

This study showed that around 7% of capsule sutures used in primary THA were contaminated with bacteria and as such exchange by new sutures at the time of capsule closure could be an appealing PJI preventive measure. However, since similar contamination rates were encountered with mainly non-virulent bacteria for both suture groups, the PJI preventive effect of this measure appears to be minimal.

External Validation of Prediction Models for Surgical Complications in People Considering Total Hip or Knee Arthroplasty Was Successful for Delirium but Not for Surgical Site Infection, Postoperative Bleeding, and Nerve Damage: A Retrospective Cohort Study

Although several models for the prediction of surgical complications after primary total hip or total knee replacement (THA and TKA, respectively) are available, only a few models have been externally validated. The aim of this study was to externally validate four previously developed models for the prediction of surgical complications in people considering primary THA or TKA. We included 2614 patients who underwent primary THA or TKA in secondary care between 2017 and 2020. Individual predicted probabilities of the risk for surgical complication per outcome (i.e., surgical site infection, postoperative bleeding, delirium, and nerve damage) were calculated for each model. The discriminative performance of patients with and without the outcome was assessed with the area under the receiver operating characteristic curve (AUC), and predictive performance was assessed with calibration plots. The predicted risk for all models varied between <0.01 and 33.5%. Good discriminative performance was found for the model for delirium with an AUC of 84% (95% CI of 0.82-0.87). For all other outcomes, poor discriminative performance was found; 55% (95% CI of 0.52-0.58) for the model for surgical site infection, 61% (95% CI of 0.59-0.64) for the model for postoperative bleeding, and 57% (95% CI of 0.53-0.61) for the model for nerve damage. Calibration of the model for delirium was moderate, resulting in an underestimation of the actual probability between 2 and 6%, and exceeding 8%. Calibration of all other models was poor. Our external validation of four internally validated prediction models for surgical complications after THA and TKA demonstrated a lack of predictive accuracy when applied in another Dutch hospital population, with the exception of the model for delirium. This model included age, the presence of a heart disease, and the presence of a disease of the central nervous system as predictor variables. We recommend that clinicians use this simple and straightforward delirium model during preoperative counselling, shared decision-making, and early delirium precautionary interventions.

The (un)necessity of regular postoperative follow-up of hemiarthroplasty for femoral neck fractures

BACKGROUND

Postoperative follow-up after hemiarthroplasty is part of routine based practice. However, these visits appear to be a significant burden since it concerns a frail population. The aim of this study was to confirm the current common practice regarding postoperative visits of patients treated with hemiarthroplasty and to evaluate the complication detection rate at these visits.

METHODS

A national short survey was conducted among orthopedic surgeons working in 26 large Dutch teaching hospitals to test the hypothesis that postoperative follow-up is indeed common practice. Furthermore, a retrospective patient review was performed in all hemiarthroplasties implanted between January 2014 and December 2019.

RESULTS

The response of the national survey was complete and showed that postoperative follow-up in patients treated with hemiarthroplasty is part of standard care according to 89% of respondents. A total of 1055 hips (1026 patients) were implanted with hemiarthroplasty during the studied period. Implant-related complications were identified in 68 hemiarthroplasties, with 31 of these hips going on to reoperation. Only 2 of these complications were picked up at standard planned follow-up leading to a complication detection rate of 0.3%. In contrast, complication detection rates of 47% and 16% were found at unplanned visits at the Emergency Department and the outpatient department, respectively.

CONCLUSIONS

Postoperative follow-up in patients treated with hemiarthroplasty is still the standard of care. However, this study revealed that the majority of implant-related complications are detected at unplanned visits and almost no at standard follow-up visits. Postoperative follow-up of patients treated with hemiarthroplasty could be abandoned in this frail population.

Preoperative Staphylococcus aureus screening and eradication

AIMS

Preoperative nasal Staphylococcus aureus screening and eradication reduces surgical site infections (SSIs) but its impact on reducing early prosthetic joint infection (PJI) remains controversial. This study aims to assess the effect of preoperative nasal S. aureus screening and eradication on the incidence of early PJI in general and S. aureus-induced early PJI.

METHODS

All primary total hip arthroplasties (THA) and total knee arthroplasties (TKA) performed from January 2006 to April 2018 were retrospectively reviewed for the incidence of early PJI. Demographic parameters, risk factors for PJI (American Society of Anaesthesiologists classification, body mass index, smoking status, and diabetes mellitus) and implant types were collected. A preoperative screening and eradication protocol for nasal colonization of S. aureus was introduced in October 2010. The incidence of early PJI was compared before and after the implementation of the protocol. Missing data were imputed via multiple imputation by chained equations. Inverse probability weighting was used to account for differences between patients in both groups. Weighted univariate logistic regression was used to evaluate the incidence of early PJI for both groups.

RESULTS

In total, 10,486 THAs and TKAs were performed in the research period. After exclusion, a cohort of 5,499 screened cases and 3,563 non-screened cases were available for analysis. Overall, no significant reduction in early PJI was found in the screened group (odds ratio (OR) 0.78, 95% confidence interval (CI) 0.55 to 1.11; p = 0.173). However, the incidence of S. aureus-induced PJI was significantly reduced (OR 0.58, 95% CI 0.36 to 0.92; p = 0.027) in the screened group.

CONCLUSION

A preoperative nasal S. aureus screening and eradication protocol did not significantly reduce the overall incidence of early PJI after THA or TKA. However, a decreased incidence of S. aureus-induced early PJI was established. These findings can help to establish better consensus around the value of these screening protocols. Cite this article: Bone Joint J 2020;102-B(10):1341-1348.

General anesthesia might be associated with early periprosthetic joint infection: an observational study of 3,909 arthroplasties

Background and purpose - Periprosthetic joint infection (PJI) remains a devastating complication following total knee or total hip arthroplasty (TKA/THA). Nowadays, many studies focus on preventive strategies regarding PJI; however, the potential role of anesthesia in the development of PJI remains unclear.Patients and methods - All consecutive patients undergoing elective primary unilateral TKA or THA from January 2014 through December 2017 were included. Exclusion criteria included femoral fractures as the indication for surgery and previously performed osteosynthesis or hardware removal on the affected joint. Age, sex, BMI, ASA classification, type of arthroplasty surgery, type of anesthesia, duration of surgery, smoking status, and intraoperative hypothermia were recorded. Propensity score-matched univariable logistic regression analysis was used to control for allocation bias.Results - 3,909 procedures consisting of 54% THAs and 46% TKAs were available for analysis. 42% arthroplasties were performed under general anesthesia and 58% under spinal anesthesia. Early PJIs were observed in 1.7% of the general anesthesia group and in 0.8% in the spinal anesthesia group. The multivariable logistic regression model demonstrated an odds ratio for PJI of 2.0 (95% CI 1.0-3.7) after general anesthesia relative to the propensity score-matched patients who received spinal anesthesia.Interpretation - These results suggest a potential association between general anesthesia and early PJI. Future research using large-scale data is required to further elucidate this clinically relevant association.

OP-1 Compared with Iliac Crest Autograft in Instrumented Posterolateral Fusion: A Randomized, Multicenter Non-Inferiority Trial

BACKGROUND

Spinal fusion with the use of autograft is a commonly performed procedure. However, harvesting of bone from the iliac crest is associated with complications. Bone morphogenetic proteins (BMPs) are extensively used as alternatives, often without sufficient evidence of safety and efficacy. The purpose of this study was to investigate non-inferiority of osteogenic protein-1 (OP-1, also known as BMP-7) in comparison with iliac crest bone graft in posterolateral fusions.

METHODS

This study was a randomized, controlled multicenter trial. Patients who underwent a single-level instrumented posterolateral fusion of the lumbar spine for degenerative or isthmic spondylolisthesis with symptoms of neurological compression were randomized to receive OP-1 combined with local bone (OP-1 group) or autologous bone graft from the iliac crest combined with local bone (autograft group). The primary outcome was overall success, defined as a combination of clinical success and evidence of fusion on computed tomography (CT) scans, at one year postoperatively.

RESULTS

One hundred and nineteen patients were included in the study, and analysis of the overall outcome was performed for 113. Non-inferiority of OP-1 compared with iliac crest autograft was not found at one year, with a success rate of 40% in the OP-1 group versus 54% in the autograft group (risk difference = -13.3%, 90% confidence interval [CI] = -28.6% to +2.10%). This was due to the lower rate of fusion (the primary aim of OP-1 application) seen on the CT scans in the OP-1 group (54% versus 74% in the autograft group, p = 0.03). There were no adverse events that could be directly related to the use of OP-1.

CONCLUSIONS

OP-1 with a collagen carrier was not as effective as autologous iliac crest bone for achieving fusion and cannot be recommended in instrumented posterolateral lumbar fusion procedures.

LEVEL OF EVIDENCE

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

Changes in bone mineral density and femoral neck narrowing in the proximal femur three to five years after hip resurfacing versus conventional total hip arthroplasty

We studied whether bone mineral density (BMD) is preserved without significant femoral neck narrowing (FNN) after hip resurfacing (RHA) (n=42) versus small diameter metal-on-metal total hip arthroplasty (MoM THA) (n=40). In this three to five year randomized trial BMD was measured in the calcar with dual energy absorptiometry (DXA) preoperatively, at three and six months, one, two, three and five years postoperatively. Four additional BMD regions of interest (ROIs) and femoral neck narrowing (FNN) were measured after RHA. BMD in the calcar increased to 107% (P<0.001) at one year and remained stable. Additional ROIs in the femoral neck and trochanter-area BMD changes fluctuated between 99.9% and 104.1%. FNN was minimal with a mean of 1.3% at three years. After THA BMD decreased in the calcar to 80% at one year (P<0.001) and stabilized. This bone stock preserving nature of RHA must be weighed against potential disadvantages caused by specific metal-on-metal bearing problems.

Metal ion levels and functional results following resurfacing hip arthroplasty versus conventional small-diameter metal-on-metal total hip arthroplasty; a 3 to 5year follow-up of a randomized controlled trial

We present an update of a randomized controlled trial on 71 patients (<65 years) who received either a resurfacing hip arthroplasty (RHA) (n=38) or cementless 28-mm metal-on-metal (MoM) total hip arthroplasty (THA) (n=33). Metal ion levels and functional outcome scores were analyzed with a mean follow-up of 58 months (SD 8.1). No clear shifts in relatively good outcome was encountered between RHA and THA. Metal ion levels appear to equalize between groups after 3 years. Median cobalt and chromium remained below 1.3 μg/L throughout follow-up in both groups. Six revisions were performed, of which three for pseudotumor formation (one THA, two RHA). In conclusion there were no clinical differences between the two groups and metal ion levels were lower than other series remained low, however, pseudotumor formation was not eliminated.

Excessive polyethylene wear and acetabular bone defects from standard use of a hooded acetabular insert in total hip arthroplasty

PURPOSE

In total hip arthroplasty (THA) the use of a polyethylene (PE) insert with a hooded rim can be considered to reduce dislocation risks. This benefit has to be balanced against the potential introduction of impingement of the femoral component on this rim. We present a case series of early acetabular revisions for excessive PE wear and acetabular bone defects from overuse of such a hooded rim insert.

MATERIAL AND METHODS

Twenty-eight patients with 34 consecutive early acetabular revisions were evaluated on failure mechanism. One type of implant was used in all cases. Standard pelvic radiographs and pre-operative CT scans were used to quantify PE wear, implant positioning and acetabular bone defects.

RESULTS

An acetabular revision with impaction grafting was performed in all cases with a mean cup survival of ten years (range 1.3-19.3). No concurrent stem revisions were necessary. Overall implant positioning was adequate with a mean cup inclination of 45° (range 39-57) and anteversion of 25° (range eight to 45). The mean PE wear was 0.24 mm/year (range 0.00-1.17). The mean acetabular bone defect on pelvic CT scans was calculated as 352 mm² (range zero to 1107) and 369 mm² (range zero to 1300) in the coronal and transversal planes, respectively. A hooded acetabular insert was retrieved in all cases and profound PE wear, typically from the posterior hooded rim, was encountered.

CONCLUSION

The use of hooded acetabular inserts may be considered to improve implant stability intra-operatively. This case series clearly presents that together with these devices, component impingement with concordant complications such as accelerated PE wear may be introduced. Standard use of these stabilizing inserts should thus be avoided.

No correlation between slip reduction in low-grade spondylolisthesis or change in neuroforaminal morphology and clinical outcome

Background

In instrumented posterolateral fusion reduction of a spondylolisthesis is appealing on theoretical grounds since this may lead to indirect decompression of the entrapped nerve roots. However, there is no consensus in the literature whether a beneficial effect of reduction on outcome can be expected. The objective of the current study was to evaluate whether a correlation between the extent of listhesis reduction and clinical improvement could be established.

Methods

From two ongoing prospective studies 72 patients with a single-level instrumented posterolateral lumbar fusion for low-grade spondylolisthesis (isthmic/degenerative 51/21) were evaluated. Radiographs and clinical outcome scores were available at baseline, 6 weeks and 1 year after surgery. Changes in neuroforaminal morphology were measured on calibrated radiographs. These changes in radiographic parameters were correlated to clinical outcome (Visual Analogue Score (VAS) leg pain, Oswestry Disability Index (ODI)). Fusion status was assessed on Computed Tomography-scan at one year.

Results

A mean spondylolisthesis of 25 percent was reduced to 15 percent at 6 weeks with some loss of reduction to 17 percent at one year. The VAS and ODI significantly improved at both time intervals after surgery (p < 0.001). No significant correlations could be established between the extent of slip reduction and improvement in VAS or ODI (Pearson’s correlation −0.2 and 0.07 respectively at one year); this also accounted for the other radiographic parameters. A fusion rate of 64 percent was seen on CT-scan.

Conclusions

Clinical outcome was not related to the obtained radiographic reduction of the slipped vertebra in patients with a lumbar fusion for low grade spondylolisthesis. Loss of reduction or non-union on CT-scans had no effect on the clinical outcome. Reduction of a low-grade spondylolisthesis in spinal fusion is appealing, however, there is no evidence that it positively affects clinical outcome on the short term.

Trial registration

ISRCTN43648350

Periacetabular bone mineral density changes after resurfacing hip arthroplasty versus conventional total hip arthroplasty. A randomized controlled DEXA study

A randomized controlled trial was performed to evaluate acetabular bone mineral density (BMD) changes after hip resurfacing (RHA) versus an established conventional total hip arthroplasty (THA). A total of 71 patients were allocated randomly to receive either an RHA press-fit cobalt-chromium cup (n=38) or a THA with a threaded titanium cup and polyethylene-metal-inlay insert (n=33). The BMD in five separate periacetabular regions of interest (ROI) was prospectively quantified preoperative until 24 months. We conclude that, in contrast to our hypothesis, periacetabular BMD was better preserved after RHA than after placement of a conventional THA. Long term follow-up studies are necessary to see whether this benefit in bone preservation sustains over longer time periods and whether it is turned into clinical benefits at future revision surgery.

Bone scintigraphy after osteochondral autograft transplantation in the knee: 13 patients followed for 4 years

BACKGROUND AND PURPOSE

Autologous osteochondral transplantation (OCT) is an established method of treating articular cartilage defects in the knee. However, the potential for donor site morbidity remains a concern. Both the restoration of the original cartilage defect and the evolution of the donor site defects can be evaluated by bone scintigraphy. Thus, we performed a prospective bone scintigraphic evaluation in patients who were treated with OCT.

PATIENTS AND METHODS

In 13 patients with a symptomatic articular cartilage defect, bone scintigraphies were obtained preoperatively, 1 year after osteochondral transplantation, and finally at an average follow-up of 4 (2.5-5.5) years. The evolution of scintigraphic activity was evaluated for both the recipient and the donor site. Parallel, clinical scoring was performed using the Lysholm knee scoring scale, the Cincinnati knee rating system, and the Tegner activity score.

RESULTS

The bone scintigraphic uptake was elevated at the involved femoral condyle preoperatively, and gradually decreased to normal levels in 7 of 11 cases. The originally normal uptake at the trochlea increased 1 year after transplantation. Then, a gradual decrease in uptake occurred again at this donor site to remain elevated at the final scintigraphy. A correlation was found between elevated scintigraphic activity and the presence of retropatellar crepitus. The mean Lysholm and Cincinnati scores had increased 1 year after transplantation. The mean Tegner score had increased 3 years after transplantation.

INTERPRETATION

Elevated bone scintigraphic activity from an osteochondral lesion in the knee can be restored with OCT. However, increased scintigraphic activity is introduced at the donor site, which becomes reduced with longer follow-up. The use of fairly large osteochondral plugs appears to correlate with retropatellar crepitus and increased scintigraphic activity, and is not therefore recommended.

A pedicle subtraction osteotomy as an adjunctive tool in the surgical treatment of a rigid thoracolumbar hyperkyphosis; a preliminary report

BACKGROUND CONTEXT

A pedicle subtraction osteotomy can be considered as part of the surgical treatment of a symptomatic sagittal imbalance. The literature on the use of this technique is limited and thus far not applied to a rigid thoracolumbar hyperkyphosis.

PURPOSE

To evaluate our preliminary results of a pedicle subtraction osteotomy as an adjunctive tool in the surgical treatment of thoracolumbar kyphotic deformities.

STUDY DESIGN/SETTING

Case series

METHODS

Eleven patients with a symptomatic kyphotic deformity were treated with a thoracolumbar pedicle subtraction osteotomy in combination with a multilevel correction. The mean follow-up was 42.8 months (range 26-105). The clinical outcome, radiographic correction, and perioperative complications were analyzed. The results in six more traditional indications (ankylosing spondylitis, kyphoscoliosis, congenital and posttraumatic deformity), were compared with the results in a subgroup of five cases with a rigid thoracolumbar hyperkyphosis.

RESULTS

All patients had a kyphotic thoracolumbar junction. An average of 5.8 levels was involved in the corrective fusion. A pedicle subtraction was always performed between the level Th10 and L2 to correct the sagittal balance. A lordotic correction of 38.8 (range 25-49) degrees was established with this fusion. The osteotomy contributed 66% (26.9 degrees) of the correction, whereas the remaining correction came from multilevel facetectomies. The visual analogue scale for both pain and impairment improved significantly (p<.005) for the entire group. Statistical analysis on the results for both subgroups separately was inappropriate because of the small number of patients available; however, overall both subgroups appeared to do equally well. All patients were very satisfied with the result and would choose surgical treatment again. No major complications were encountered.

CONCLUSIONS

A pedicle subtraction osteotomy is a technically demanding but well tolerated operative procedure for the correction of a kyphotic deformity. This technique can also be considered as an adjunctive tool in the surgical treatment of a rigid thoracolumbar (Scheuermann's) kyphosis.

Anterior cervical interbody fusion with radiolucent carbon fiber cages: clinical and radiological results

The authors retrospectively evaluated 30 patients with an anterior cervical interbody fusion for cervical spondylosis or disc herniation. Open box carbon fiber cages were used at 45 levels. The visual analogue scales (VAS), respectively for neck and for arm pain, and the neck disability index (NDI) improved significantly (p < 0.001). Fusion occurred in 87% of the operated levels. Subsidence of the cages into the endplates was observed in 49% of the operated levels, which increased to 54% when more levels were fused. No correlation between subsidence of the cage and clinical outcome or radiographic fusion was established. The authors conclude that cervical discectomy and interbody fusion using an open box carbon fiber cage is a satisfactory treatment option for degenerative cervical disease causing neck pain and radiculopathy, despite the relatively high percentage of subsidence of this cage.

Transient kyphotic deformity of the thoracolumbar junction resulting from a large abdominal cyst: a case report

BACKGROUND CONTEXT

Pronounced kyphosis of the thoracolumbar junction is a common orthopedic problem in adolescents and may require prolonged bracing therapy or correction spondylodesis.

PURPOSE

To describe a case where a kyphotic deformity was related to gynecological instead of spine pathology.

STUDY DESIGN

Case report.

METHODS

A 17-year-old girl presented with a structural hyperkyphosis of the thoracolumbar spine and radiographic changes of the involved vertebral end plates.

RESULTS

The thoracolumbar hyperkyphosis appeared to have evolved from a massive intra-abdominal ovarian cyst. Endoscopic paracentesis of the cyst resulted in a complete regression of the hyperkyphosis.

CONCLUSIONS

A hyperkyphosis is not always related to spine pathology, and other potential causes must be excluded before bracing therapy is initiated.

Potential healing benefit of an osteoperiosteal bone plug from the proximal tibia on a mosaicplasty donor-site defect in the knee. An experimental study in the goat

INTRODUCTION

Autologous osteochondral transplantation is a popular treatment for articular cartilage lesions in the knee joint. The donor defect is commonly left empty and remains a matter of concern.

MATERIALS AND METHODS

In 20 knees of 10 goats, we created a standardised donor defect in the knee. In the control group the defects were left empty, whereas in two other groups a bone plug from the proximal tibia was press-fitted into the defect with or without a covering periosteal layer.

RESULTS

Histological evaluation after 8 and 16 weeks showed that relatively rapid osteoclastic resorption of the bone plug occurred. Defects were mainly filled with fibrous tissue, and collapse of the adjacent bone and cartilage was visible, especially when the defects were left empty. Occasionally, some consolidation of the graft to the host bone could be detected, and in some samples periosteal chondrogenesis was present.

CONCLUSION

Our findings suggest that transplantation of a tibial bone plug with covering periosteum to the donor defect in a cartilage transplantation procedure does not have any additional value in an attempt to minimise the damage at the donor site. The observed resorption of the bone plug and the collapse of the adjacent joint margin remain a matter of concern with this technique.

Cross-linked type I and type II collagenous matrices for the repair of full-thickness articular cartilage defects--a study in rabbits

The physico-chemical properties of collagenous matrices may determine the tissue response after insertion into full-thickness articular cartilage defects. In this study, cross-linked type I and type II collagen matrices, with and without attached chondroitin sulfate, were implanted into full-thickness defects in the femoral trochlea of adolescent rabbits. The tissue response was evaluated 4 and 12 weeks after implantation by general histology and two semi-quantitative histological grading systems. Four weeks after implantation, type I collagenous matrices were completely filled with cartilage-like tissue. By contrast, type II collagenous matrices revealed predominantly cartilaginous tissue only at the superficial zone and at the interface of the matrix with the subchondral bone, leaving large areas of the matrix devoid of tissue. Attachment of chondroitin sulfate appeared to promote cellular ingrowth and cartilaginous tissue formation in both types of collagen matrices. Twelve weeks after implantation, the differences between the matrices were less pronounced. The deep parts of the subchondral defects were largely replaced by new bone with a concomitant degradation of the matrices. The original cartilage contours in defects with type I collagen-based matrices were repaired with fibro-cartilaginous tissue. Defects containing type II matrices showed an increase in the amount of superficial cartilage-like tissue. The original contour, however, was not completely restored in all animals, occasionally leaving a central depression or fissure. It is concluded that different types of collagen matrices induce different tissue responses in full-thickness articular cartilage defects. Type I collagen-based matrices are superior to guide progenitor cells from a subchondral origin into the defect. In type II collagen-based matrices cell migration is less, but invading cells are directed into a chondrocyte phenotype. Based on these observations it is suggested that a composite matrix consisting of a deep layer of type I collagen and a more superficial layer of type II collagen may be the matrix of choice for cartilage regeneration.