Postfasciotomy Classification System for Acute Compartment Syndrome of the Leg.

OBJECTIVE: Acute compartment syndrome (ACS) is a true emergency. Even with urgent fasciotomy, there is often muscle damage and need for further surgery. Although ACS is not uncommon, no validated classification system exists to aid in efficient and clear communication. The aim of this study was to establish and validate a classification system for the consequences of ACS treated with fasciotomy. METHODS: Using a modified Delphi method, an international panel of ACS experts was assembled to establish a grading scheme for the disease and then validate the classification system. The goal was to articulate discrete grades of ACS related to fasciotomy findings and associated costs. A pilot analysis was used to determine questions that were clear to the respondents. Discussion of this analysis resulted in another round of cases used for 24 other raters. The 24 individuals implemented the classification system 2 separate times to compare outcomes for 32 clinical cases. The accuracy and reproducibility of the classification system were subsequently calculated based on the providers' responses. RESULTS: The Fleiss Kappa of all raters was at 0.711, showing a strong agreement between the 24 raters. Secondary validation was performed for paired 276 raters and correlation was tested using the Kendall coefficient. The median correlation coefficient was 0.855. All 276 pairs had statistically significant correlation. Correlation coefficient between the first and second rating sessions was strong with the median pair scoring at 0.867. All surgeons had statistically significant internal consistency. CONCLUSION: This new ACS classification system may be applied to better understand the impact of ACS on patient outcomes and economic costs for leg ACS.

In reply to the letter to the editor regarding "Comparison of a twin interlocking derotation and compression screw cephalomedullary nail (InterTAN) with a single screw derotation cephalomedullary nail (proximal femoral nail antirotation): a systematic review and meta-analysis for intertrochanteric fractures".

BACKGROUND: Intertrochanteric hip fractures are common and devastating injuries, especially for the elderly. Surgical treatment is the optimal strategy for managing intertrochanteric fractures as it allows early rehabilitation and functional recovery. The relative effects of internal fixation strategies for intertrochanteric fracture after operation remain limited to relatively small studies which create uncertainty in attempts to establish evidence-based best practice. METHODS: We conducted a systematic review and meta-analysis of randomised controlled trials (RCTs) and observational studies to assess the clinical effectiveness of two commonly used intramedullary devices: a twin-screw integrated cephalomedullary nail (InterTAN) versus a single-screw cephalomedullary nail (proximal femoral nail antirotation) in patients with intertrochanteric fractures. The following outcomes were considered: revisions, implant-related failures, non-unions, pain, Harris hip score and intra-operative outcomes. Odds ratios or mean differences with 95% confidence intervals in brackets are reported. RESULTS: Six studies met the inclusion criteria: two randomised controlled trials and four observational studies enrolling 970 patients with a mean age of 77 years and 64% of patients being female. There was a statistically significant difference (p value < 0.05) for revisions OR 0.27 (0.13-0.56), implant-related failures OR 0.16 (0.09-0.27) and proportion of patients complaining of pain OR 0.50 (0.34-0.74). There was no difference in non-unions and Harris hip score (p value > 0.05). There was a significant difference in blood loss and fluoroscopy usage in favour of PFNA, while no difference in operating times was observed between the two devices. CONCLUSIONS: Our meta-analysis suggests that a twin-screw integrated cephalomedullary nail (InterTAN) is clinically more effective when compared to a single-screw cephalomedullary nail proximal femoral nail antirotation resulting in fewer complications, fewer revisions and fewer patients complaining of pain. No difference has been established regarding non-unions and Harris hip score. Intra-operative outcomes favour PFNA with less blood loss and fluoroscopy usage. Further studies are warranted to explore the cost-effectiveness of these and other implants in managing patients with intertrochanteric fractures.

Real time measurement of intramuscular pH during routine knee arthroscopy using a tourniquet : a preliminary study.

AIMS: Tourniquets have potential adverse effects including postoperative thigh pain, likely caused by their ischaemic and possible compressive effects. The aims of this preliminary study were to determine if it is possible to directly measure intramuscular pH in human subjects over time, and to measure the intramuscular pH changes resulting from tourniquet ischaemia in patients undergoing knee arthroscopy. METHODS: For patients undergoing short knee arthroscopic procedures, a sterile calibrated pH probe was inserted into the anterior fascial compartment of the leg after skin preparation, but before tourniquet inflation. The limb was elevated for three minutes prior to tourniquet inflation to 250 mmHg or 300 mmHg. Intramuscular pH was recorded at one-second intervals throughout the procedure and for 20 minutes following tourniquet deflation. Probe-related adverse events were recorded. RESULTS: A total of 27 patients were recruited to the study. Mean tourniquet time was 21 minutes (10 to 56). Tourniquet pressure was 300 mmHg for 21 patients and 250 mmHg for six patients. Mean muscle pH prior to tourniquet inflation was 6.80. Muscle pH decreased upon tourniquet inflation, with a steeper fall in the first ten minutes than for the rest of the procedure. Change in muscle pH was significant after five minutes of tourniquet ischaemia (p < 0.001). Mean muscle pH prior to tourniquet release was 6.58 and recovered to 6.75 within 20 minutes following release. No probe related adverse events were recorded. CONCLUSION: It is possible to directly measure skeletal muscle pH in human subjects over time. Tourniquet ischaemia results in a decrease in human skeletal muscle pH over time during short procedures. Cite this article: Bone Joint Res 2021;10(6):363-369.

Diagnosing acute compartment syndrome-where have we got to?

PURPOSE: Acute compartment syndrome is a condition whereby tissue ischaemia occurs due to increased pressure in a closed myofascial compartment. It is a surgical emergency, with rapid recognition and treatment-the keys to good outcomes. METHODS: The available literature on diagnostic aids was reviewed by one of the senior authors 15 years ago. Now, we have further reviewed the literature, to aim to ascertain what progress has been made. RESULTS: In this review, we present the evidence around a variety of available diagnostic options when investigating a potential case of acute compartment syndrome, including those looking at pressure changes, localised oxygenation, perfusion, metabolic changes and available blood serum biomarkers. CONCLUSIONS: A significant amount of work has been put into developing modalities of diagnosis for acute compartment syndrome in the last 15 years. There is a lot of promising outcomes being reported; however, there is yet to be any conclusive evidence to suggest that they should be used over intracompartmental pressure measurement, which remains the gold standard. However, clinicians should be cognizant that compartment pressure monitoring lacks diagnostic specificity, and could lead to unnecessary fasciotomy when used as the sole criterion for diagnosis. Therefore, pressure monitoring is ideally used in situations where clinical suspicion is raised.

Uniting the un-united: should established non-unions of femoral shaft fractures initially treated with IM nails be treated by plate augmentation instead of exchange IM nailing? A systematic review.

The majority of femoral fractures are surgically treated with intramedullary nails. Non-union rate is low but challenging and costly if it occurs. There have been encouraging results from the use of augmentative plating as a treatment for non-union of femoral fractures. We performed a systematic review of the literature to compare union rates, time to union and complications between exchange nailing and augmentative plating as a primary procedure following a diagnosis of femoral non-union following initial nailing. We found a total of 21 papers, which found the mean union rate of augmentative plating to be 99.8% compared to 74% (P = 2.05-12) found for exchange nailing. Times to union were comparable at 5.9 months for augmentative plating and 6.3 months for exchange nailing (P = 0.68916), and complication rate was 4% for augmentative plating compared to 20% for exchange nailing. From the evidence available, plate augmentation provides a more reliable union rate if used as the first operative intervention on a non-union of a femoral fracture compared to exchange nailing.Level of Evidence IV Systematic review of therapeutic studies.

Comparing the costs and outcomes of an integrated twin compression screw (ITCS) nail with standard of care using a single lag screw or a single helical blade cephalomedullary nail in patients with intertrochanteric hip fractures.

BACKGROUND: Surgical treatment is the optimal strategy for managing intertrochanteric fractures as it allows for early rehabilitation and functional recovery. The purpose of the study was to assess the cost-effectiveness of commonly used cephalomedullary nails for the treatment of unstable intertrochanteric hip fractures. METHODS: A decision analytic model was developed from a US payer's perspective using clinical data from a pairwise meta-analysis of randomised controlled trials (RCTs) and comparative observational studies comparing the integrated twin compression screw (ITCS) nail versus two single-screw or blade cephalomedullary nails [single lag screw (SLS) nail and single helical blade (SHB) nail]. The model considered a cohort of 1000 patients with a mean age of 76, as reported in the clinical studies over a 1-year time period. Cost data was obtained from the Center for Medicare and Medicaid Services website and published literature and adjusted for inflation. One-way and probabilistic sensitivity analyses were conducted to assess the effect of uncertainty in model parameters on model conclusions. RESULTS: The model estimated 0.546 quality-adjusted life years (QALYs) and 0.78 complications avoided by using the ITCS nail and 0.455 QALYs and 0.67 complications avoided for the standard of care, using SLS or SHB nails. The cost per patient was $34,336 for patients treated with an ITCS nail and $37,036 for patients treated with the standard of care respectively, resulting in a cost saving of $2700 in favour of the ITCS nail. More savings were observed when the ITCS nail was compared to the SHB ($3280 per patient) and SLS ($1652 per patient). The findings were robust to a range of both one-way and the probabilistic sensitivity analyses. CONCLUSION: In conclusion, the ITCS nail can be considered a cost saving intervention in patients undergoing intertrochanteric fracture fixation with an intramedullary device. Clinicians and policy makers should be encouraged to adopt healthcare technologies such as ITCS that will help them to provide quality healthcare despite falling budgets.

The implants used for intramedullary fixation of distal fibula fractures: A review of literature.

BACKGROUND: Ankle fractures are amongst the most common surgically treated musculoskeletal injuries. Intramedullary (IM) fixation of the lateral malleolus had been attempted as early as the 1990s. In recent years, dedicated implants have emerged. This review evaluates the design characteristics of the technology used to perform IM fixation of distal fibular fractures. MATERIALS AND METHODS: A search of electronic databases was performed. Medical subject headings (MeSH) and free-text terms were used to optimise search sensitivity and specificity. RESULTS: We identified 10 different surgical technologies for IM fixation of lateral malleolar fractures reported across 12 articles, including both improvised and custom-designed Orthopaedic implants. Most implants were inserted through percutaneous surgical techniques. CONCLUSION: Advances in technology have improved the feasibility of intramedullary fixation as a treatment option for lateral malleolus fractures. The implants we reviewed had very diverse morphological and mechanical properties. Intra-medullary fixation may outperform extra-medullary fixation of the lateral malleolus, particularly in patients at high risk of soft tissue complications. Robust scientific evidence is awaited. LEVEL OF EVIDENCE: Level IV evidence.

Comparison of a twin interlocking derotation and compression screw cephalomedullary nail (InterTAN) with a single screw derotation cephalomedullary nail (proximal femoral nail antirotation): a systematic review and meta-analysis for intertrochanteric fractures.

BACKGROUND: Intertrochanteric hip fractures are common and devastating injuries especially for the elderly. Surgical treatment is the optimal strategy for managing intertrochanteric fractures as it allows early rehabilitation and functional recovery. The relative effects of internal fixation strategies for intertrochanteric fracture after operation remain limited to relatively small studies which create uncertainty in attempts to establish evidence-based best practice. METHODS: We conducted a systematic review and meta-analysis of randomised controlled trials (RCTs) and observational studies to assess the clinical effectiveness of two commonly used intramedullary devices: a twin screw integrated cephalomedullary nail (InterTAN) versus a single screw cephalomedullary nail (proximal femoral nail antirotation) in patients with intertrochanteric fractures. The following outcomes were considered: revisions, implant-related failures, non-unions, pain, Harris Hip Score and intraoperative outcomes. Odds ratios or mean differences with 95% confidence intervals in brackets are reported. RESULTS: Six studies met the inclusion criteria, two randomised controlled trials and four observational studies enrolling 970 patients with mean age of 77 years, and 64% of patients were female. There was a statistically significant difference (p value < 0.05) for revisions OR 0.27 (0.13 to 0.56), implant-related failures OR 0.16 (0.09 to 0.27) and proportion of patients complaining of pain OR 0.50 (0.34 to 0.74). There was no difference in non-unions and Harris Hip Score (p value > 0.05). There was a significant difference in blood loss and fluoroscopy usage in favour of PFNA, whilst no difference in operating times were observed between the two devices. CONCLUSIONS: Our meta-analysis suggests that a twin screw integrated cephalomedullary nail InterTAN is clinically more effective when compared to a single screw cephalomedullary nail proximal femoral nail antirotation resulting in fewer complications, fewer revisions and fewer patients complaining of pain. No difference has been established regarding non-unions and Harris Hip Score. Intraoperative outcomes favour PFNA with less blood loss and fluoroscopy usage. Further studies are warranted to explore the cost-effectiveness of these and other implants in managing patients with intertrochanteric fractures.

Primary screw perforation or subsequent screw cut-out following proximal humerus fracture fixation using locking plates: a review of causative factors and proposed solutions.

The surgical treatment of proximal humerus fractures remains controversial primarily due to the high complication rate associated with the available fixation methods. In an attempt to reduce the incidence of serious complications and subsequent poor clinical outcomes, proximal humerus locking plates have become popular but even these implants cannot overcome the risk of complications, especially those associated with loss of fracture reduction and screw cut-out/migration through the humeral head. In an attempt to address these issues, we have reviewed the literature, investigating the most likely causes for these predominantly mechanical complications and propose technical solutions.

Technical considerations to avoid delayed and non-union.

For many years intramedullary nails have been a well accepted and successful method of diaphyseal fracture fixation. However, delayed and non unions with this technique do still occur and are associated with significant patient morbidity. The reason for this can be multi-factorial. We discuss a number of technical considerations to maximise fracture reduction, fracture stability and fracture vascularity in order to achieve bony union.

Percutaneous screw fixation of unstable ankle fractures in patients with poor soft tissues and significant co-morbidities.

INTRODUCTION: We describe a minimally invasive technique to stabilise unstable ankle fractures by inserting a 100mm screw up the fibula medullary canal along with percutaneous screw fixation of the medial malleolus if required. This technique is utilised in patients with poor soft tissues and significant co-morbidities where the fracture cannot be adequately controlled by a cast alone. PATIENTS AND METHODS: Retrospective review of 23 patients the average age being 70 years (29-89) and 74% had significant co-morbidities. Postoperative radiographs were examined for adequacy of reduction using the method described by Mclenna and Ungersma. Patient based functional and health questionnaires were performed, reviewed and scored. RESULTS: Six patients were lost during the follow-up period due to death caused by issues unrelated to the ankle fracture. There were no reported intraoperative complications, no postoperative wound infections and no non-unions. There was two complications one loss of fixation, and another required removal of the screw due to irritation. Radiographic reduction was good in 52%, fair in 44% and poor in 4%. Patient questionnaire results were 70 (20-100) for the Abbreviated Olerud and Molander score and the SF-12 physical component score was 42 and mental component was 44. CONCLUSIONS: With appropriate patient selection percutaneous screw fixation is an excellent technique supplementing cast immobilisation of unstable ankle fractures with poor soft tissues.

Assessment Following Distal Radius Fractures: A Comparison of 4 Scoring Systems, Visual Numerical Scales, and Objective Measurements.

PURPOSE: To compare 4 recognized upper-limb scoring systems that are regularly used to assess wrist function after injury. METHODS: We reviewed 116 patients 6 months after volar locking plate fixation for distal radius fractures. Two purely subjective and 2 composite scoring systems composed of both subjective and objective components were compared along with visual numerical scores for pain and function and objective measures of function. Each score was standardized into a scale from 0 to 100. RESULTS: The distribution of the standardized total scores was statistically significantly different and indicated marked variability between scoring systems and therefore the information provided. Overall, the subjective scoring systems correlated well with each other and with both visual numerical scores for pain and function. However, the composite scores and objective measures of function correlated poorly with the subjective scores including the visual numerical scores. CONCLUSIONS: Results from wrist scoring systems should be interpreted with caution. It is important to ensure that the component parts of each score are taken into consideration separately because total scores may be misleading. CLINICAL RELEVANCE: Composite scores may be outdated and should be avoided.

Do trauma systems work? A comparison of major trauma outcomes between Aberdeen Royal Infirmary and Massachusetts General Hospital.

Trauma is an important matter of public health and a major cause of mortality. Since the late 1980s trauma care provision in the United Kingdom is lacking when compared to the USA. This has been attributed to a lack of organisation of trauma care leading to the formation of trauma networks and Major Trauma Centres in England and Wales. The need for similar centres in Scotland is argued currently. We assessed the activity of two quite different trauma systems by obtaining access to comparative data from two hospitals, one in the USA and the other in Scotland. Aggregate data on 5604 patients at Aberdeen Royal Infirmary (ARI) from 1993 to 2002 was obtained from the Scottish Trauma Audit Group. A comparable data set of 16,178 patients from Massachusetts General Hospital (MGH). Direct comparison of patient demographics; injury type, mechanism and Injury Severity Score (ISS); mode of arrival; length of stay and mortality were made. Statistical analysis was carried out using Chi-squared and Cochran-Mantel-Haenszel. There were significant differences in the data sets. There was a higher proportion of penetrating injuries at MGH, (8.6% vs 2.6%) and more severely injured patients at MGH, patients with an ISS>16 accounted for nearly 22.1% of MGH patients compared to 14.0% at ARI. ISS 8-15 made up 54.6% of ARI trauma with 29.6% at MGH. Falls accounted for 50.1% at ARI and 37.9% at MGH. Despite the higher proportion of severe injuries at MGH and crude mortality rates showing no difference (4.9% ARI vs 5.2% MGH), pooled odds ratio of mortality was 1.4 (95% confidence interval 1.2-1.6) showing worse mortality outcomes at ARI compared to MGH. In conclusion, there were some differences in case mix between both data sets making direct comparison of the outcomes difficult, but the effect of consolidating major trauma on the proportion and number of severely injured patients treated in the American Level 1 centre was clear with a significant improvement in mortality in all injury severity groups.

In vivo temperature measurement in the subacromial bursa during arthroscopic subacromial decompression.

BACKGROUND: The purpose of the study was to evaluate whether use of a bi-polar radiofrequency (RF) ablation wand would cause excess heating, which may lead to collateral damage to the surrounding tissues during arthroscopic subacromial decompression. Cadaveric studies have shown that high temperatures can potentially be reached when using RF ablation wands in arthroscopic shoulder surgery. Only 1 other published study assesses these temperature rises in the clinical setting. METHODS: Fifteen patients were recruited to participate in the study. A standard arthroscopic subacromial decompression was performed using continuous flow irrigation, with intermittent use of the RF ablation wand for soft tissue debridement. The temperature of the irrigation fluid within the subacromial bursa and the outflow fluid from the suction port of the wand were measured during the procedure using fiber-optic thermometers. RESULTS: The mean peak temperature recorded in the subacromial bursa was 32.0°C (29.3-43.1°C), with a mean rise from baseline of 9.8°C. The mean peak temperature recorded from the outflow fluid from the wand was 71.6°C (65.6-77.6°C), with a mean rise from baseline of 49.4°C. CONCLUSION: High temperatures were noted in the outflow fluid from the wand; however, this was not evident in the subacromial bursa itself. Use of room temperature inflow fluid, maintenance of flow through the bursa, and avoidance of prolonged uninterrupted use of the wand all appear to ensure that safe temperatures are maintained in the subacromial bursa not only in the laboratory but also in a clinical setting.

Shoulder outcome measures: is there a right answer?

PURPOSE: A number of outcome measures (instruments) are used to assess shoulder pain and function in clinical practice. No clear 'gold standard' exists and it is thought that different instruments will give a different answer. Our aim is to statistically compare four commonly used outcome measures in a group of trauma patients and to identify whether instruments which combine objective and subjective components differ from those which are purely subjective. METHODS: Forty-four patients undergoing internal fixation of proximal humeral fractures were recruited between 2003 and 2008. Each was asked to complete a number of outcome measures: University of Los Angeles score (UCLA); Constant and Murley score (Constant); Oxford Shoulder Score (OSS); Quick form of the Disabilities of the Arm, Shoulder and Hand questionnaire (QuickDASH). Each were measured on a different scale but were standardised to 0-100 for comparison. RESULTS: Purely subjective instruments gave higher scores (better function and/or less pain). Statistical differences were found between each pair of instruments (p < 0.001), except for the comparison between UCLA and QuickDASH (p = 0.403). The study found inconsistencies between instruments, with outcomes varying depending on whether subjective or objective measurements were being assessed. CONCLUSIONS: Outcome measures are useful tools, but clinicians need to be aware that their choice of instrument should be made carefully, taking into account the reason behind its use with regard to outcome.

Displaced distal radial fractures treated using volar locking plates: maintenance of normal anatomy.

BACKGROUND: The objective is to assess the ability of volar locking plates to maintain fracture reduction when used to treat dorsally displaced extra- and intra-articular distal radial fractures. METHODS: This prospective study was conducted over an 12-month period. Consenting patients who had sustained a closed, dorsally displaced distal radial fracture, treated by open reduction and internal fixation using a volar distal radial locking plate were included in the study. Radial inclination, volar tilt, and ulnar variance were measured from radiographs taken at least 3 months after surgery and compared with radiographs of the uninjured side. Only two of the eight participating surgeons have a specialist interest in upper limb surgery. RESULTS: Thirty-three patients were included in the study. There were 23 women and 10 men. The mean age was 49.5 years (range, 26-82 years). According to the Orthopaedic Trauma Association (OTA) classification, there were 19 Type A, 1 Type B, and 13 Type C fractures. The average restoration of volar tilt was 1-degree angle of under correction with a range of 7.3-degree angle of under correction to 3.7-degree angle of over correction, when compared with the uninjured side. The mean restoration of radial inclination was 1.9-degree angle of under correction with a range of 10-degree angle of under correction to 8.4-degree angle of over correction. As a group, the mean ulnar variance was 0 mm with a range of 2 mm of relative ulnar shortening to 3.5 mm of ulnar prominence when compared with the uninjured side. CONCLUSION: In the hands of general trauma surgeons, the volar approach combined with the application of a suitable volar locking plate is a good treatment for restoring and maintaining the anatomy of dorsally displaced intra- and extra-articular distal radial fractures.

Attachment of human primary osteoblast cells to modified polyethylene surfaces.

Ultra-high-molecular-weight polyethylene (UHMWPE) has a long history of use in medical devices, primarily for articulating surfaces due to its inherent low surface energy which limits tissue integration. To widen the applications of UHMWPE, the surface energy can be increased. The increase in surface energy would improve the adsorption of proteins and attachment of cells to allow tissue integration, thereby allowing UHMWPE to potentially be used for a wider range of implants. The attachment and function of human primary osteoblast-like (HOB) cells to surfaces of UHMWPE with various levels of incorporated surface oxygen have been investigated. The surface modification of the UHMWPE was produced by exposure to a UV/ozone treatment. The resulting surface chemistry was studied using X-ray photoelectron spectroscopy (XPS), and the topography and surface structure were probed by atomic force microscopy (AFM) and scanning electron microscopy (SEM), which showed an increase in surface oxygen from 11 to 26 atom % with no significant change to the surface topography. The absolute root mean square roughness of both untreated and UV/ozone-treated surfaces was within 350-450 nm, and the water contact angles decreased with increasing oxygen incorporation, i.e., showing an increase in surface hydrophilicity. Cell attachment and functionality were assessed over a 21 day period for each cell-surface combination studied; these were performed using SEM and the alamarBlue assay to study cell attachment and proliferation and energy-dispersive X-ray (EDX) analysis to confirm extracellular mineral deposits, and total protein assay to examine the intra- and extracellular protein expressed by the cells. HOB cells cultured for 21 days on the modified UHMWPE surfaces with 19 and 26 atom % oxygen incorporated showed significantly higher cell densities compared to cells cultured on tissue culture polystyrene (TCPS) from day 3 onward. This indicated that the cells attached and proliferated more readily on the UV/ozone-treated UHMWPE surfaces than on untreated UHMWPE and TCPS surfaces. Contact guidance of the cells was observed on the UHMWPE surfaces by both SEM and AFM. Scanning electron micrographs showed that the cells were confluent on the modified UHMWPE surfaces by day 10, which led to visible layering of the cells by day 21, an indicator of nodule formation. In vitro mineralization of the extracellular matrix expressed by the HOB cells on the modified UHMWPE surfaces was confirmed by SEM and EDX analysis; spherulite structures were observed near cell protrusions by day 21. EDX analysis confirmed the spherulites to contain calcium and phosphorus, the major constituents in calcium phosphate apatite, the mineral phase of bone. Overall cell attachment, functionality, and mineralization were found to be enhanced on the UV/ozone-modified UHMWPE surfaces, demonstrating the importance of optimizing the surface chemistry for primary HOB cells.

Platelet derived growth factor-AB enhances knee meniscal cell activity in vitro.

Meniscal healing especially in the inner avascular region has always been a major challenge. In this study we investigated the potential for platelet derived growth factor-AB (PDGF-AB) to promote meniscal tissue regeneration in the inner (avascular), middle, and outer (vascular) zones of the meniscus. Various concentrations of PDGF-AB were tested on sheep meniscal cell cultures. We used the radioactive thymidine uptake assay to assess cell proliferation, and the radioactive sulphur and proline uptake assays and Blyscan assay to assess matrix formation. In general, PDGF-AB stimulated both cell proliferation and matrix formation by cells from all meniscal zones. PDGF-AB at a concentration of 100 ng/ml increased cell proliferation and matrix formation by eight and four fold respectively, by fibrochondrocytes cultured from all meniscal zones (p<0.001). These results indicate that fibrochondrocytes present within the avascular region of the meniscus have the ability to proliferate and form new matrix when exposed to anabolic cytokines such as PDGF-AB.