Aims

Reverse total shoulder arthroplasty (rTSA) can be used in complex cases when the glenoid requires reconstruction. In this study, a baseplate with composite bone autograft and a central trabecular titanium peg was implanted, and its migration was assessed for two years postoperatively using radiostereometric analysis (RSA).

The purpose of this study is to report the clinical and radiological outcomes of patients undergoing primary or revision reverse total shoulder arthroplasty using custom 3D printed components to manage severe glenoid bone loss with a minimum of 2-year follow-up.

After ethical approval (reference: 17/YH/0318), patients were identified and invited to participate in this observational study. Inclusion criteria included: 1) severe glenoid bone loss necessitating the need for custom implants; 2) patients with definitive glenoid and humeral components implanted more than 2 years prior; 3) ability to comply with patient reported outcome questionnaires. After seeking consent, included patients underwent clinical assessment utilising the Oxford Shoulder Score (OSS), Constant-Murley score, American Shoulder and Elbow Society Score (ASES), and quick Disabilities of the Arm, Shoulder, and Hand Score (quickDASH). Radiographic assessment included AP and axial projections. Patients were invited to attend a CT scan to confirm osseointegration. Statistical analysis utilised included descriptive statistics (mean and standard deviation) and paired t test for parametric data.

3 patients had revision surgery prior to the 2-year follow-up. Of these, 2/3 retained their custom glenoid components. 4 patients declined to participate. 5 patients were deceased at the time of commencement of the study. 21 patients were included in this analysis. The mean follow-up was 36.1 months from surgery (range 22–60.2 months). OSS improved from a mean 16 (SD 9.1) to 36 (SD 11.5) (p < 0.001). Constant-Murley score improved from mean 9 (SD 9.2) to 50 (SD 16.4) (p < 0.001). QuickDASH improved from mean 67 (SD 24) to 26 (SD 27.2) (p = 0.004). ASES improved from mean 28 (SD 24.8) to 70 (SD 23.9) (p = 0.007). Radiographic evaluation demonstrated good osseointegration in all 21 included patients.

The utility of custom 3D-printed components for managing severe glenoid bone loss in primary and revision reverse total shoulder arthroplasty yields significant clinical improvements in this complex patient cohort.

Aims

We present our experience of using a metal-backed prosthesis and autologous bone graft to treat gross glenoid bone deficiency.

In previously published work, MR arthrogram (MRA) has sensitivities and specificities of 88–100% and 89–93% respectively in detection of glenoid labrum tears. Our practice suggested higher frequency of falsely negative reports. We aimed to assess accuracy of this costly modality in practice.

We retrospectively reviewed MRA reports of 90 consecutive patients with clinical shoulder instability who had undergone arthroscopy. All had history of traumatic anterior dislocation and had positive anterior apprehension tests. All underwent stabilisation during the same procedure. We compared the findings, using arthoscopy as gold standard in identification of glenoid labral tears.

83/90 patients had glenoid labrum tears at arthroscopy. Only 54 were correctly identified at MRA. All normal labra were identified. This gave sensitivity of 65% and specificity of 100% in identification of all types of glenoid labrum tear. The majority had anterior glenoid labral tears, which were detected at an even lower rate of sensitivity (58%).

Sensitivity of MRA in this series is significantly lower than previously published. This study highlights the importance of an accurate history and clinical examination by specialist shoulder surgeons in the management of glenohumeral instability. The need for this costly investigation may not be as high as is currently the case.

Long-term prospective RCT comparing hemiarthroplasty (HEMI) and total hip arthroplasty (THA) for the treatment of intracapsular neck of femur fracture.

81 previously mobile, independent, orientated patients were randomised to receive THA or HEMI after sustaining a displaced neck of femur fracture. Patients were followed up with radiographs, Oxford hip score (OHS), SF-36 scores and their walking distance.

At a mean follow up of 8.7 years, overall mortality following THA was 32.5% compared to 51.2% following HEMI (p=0.09). Following THA, patients died after a mean of 63.6 months compared to 45 months following HEMI (p=0.093). Patients with THA walked further and had better physical function. No HEMIs dislocated but three (7.5%) THAs did. Four (9.8%) HEMI patients were revised to THA, but only one (2.5%) THA required revision. All surviving HEMI patients had acetabular erosion and all surviving THA patients had wear of the cemented polyethylene cup.

Patients with THA have better function in the medium-term and survive longer.

Introduction: We report on the long-term follow up of a previously published randomised controlled trial comparing Hemiarthroplasty (HEMI) and total hip arthroplasty (THA) for the treatment of intracapsular fracture neck of femur.

Methods: In this prospectively randomized study, 81 patients who had been mobile and lived independently and who sustained a displaced fracture of the femoral neck were randomized to receive either a fixed acetabular component THA or HEMI. The mean age of the study group was 75 years at fracture. All patients received the same cemented collarless tapered femoral stem and all procedures were performed through a transgluteal approach. Patients were followed up with radiographs, Oxford hip score (OHS), SF-36, Euroqol and their walking distance.

Results: At a mean follow-up of 8.6 years (7.18 to 10.27), 19 HEMI patients and 27 THA were alive (p=0.042). The mean walking distance of patients after HEMI was 600m and the OHS 21. After THA, the mean walking distance was 1200m and the OHS was 22. Both groups had a deterioration of their OHS over time. There were no significant differences between the groups with respect to both physical and mental component SF-36 scores and Euroqol visual analogue scores.

Of the survivors four of the HEMI group were revised to total hip arthroplasty. One patient had been revised in the THA group. Radiographically six of seven patients in the HEMI group had evidence of acetabular erosion and 13 of 15 patients in the THA group had a lucency around their acetabular component.

Discussion: Patients with THA walked further and survived longer. After a mean of nine years follow up there was no difference with respect to function as measured by OHS, Euroqol and SF-36 scores.

Use of epidural analgesia post-operatively in spinal surgery is becoming increasingly common. We have conducted a prospective study examining the side-effects associated with epidurals and the need for additional analgesia in 36 adult patients undergoing either lumbar spine decompression, lumbar spine fusion, or a combination of decompression and fusion. A mixture of bupivacaine and fentanyl was used for up to 72 hours post-operatively via an epidural catheter placed under direct vision at the time of surgery. All patients had urinary catheters inserted peri-operatively.

15 patients experienced one or more side-effects; 6 patients had a subjectively unpleasant sensory block, 3 patients developed a motor block, 4 patients had pruritus, 3 developed hypotension, and 2 had episodes of nausea or vomiting. All these features resolved upon reduction of the epidural rate or cessation of the epidural. All patients required additional oral analgesia at some point during their observation. There were no serious complications, such as infection, permanent neurological deficit, or cord compression.

We conclude epidural analgesia following lumbar spine surgery is a safe practice, although the high rate of side-effects necessitates close observation by fully trained staff. It appears additional oral analgesia is required to obtain satisfactory levels of analgesia.

Objectives: This study aims to assess the psychological profile of patients prior to total knee replacement, medial unicompartmental knee replacement and patellofemoral joint replacement and determine its effect on outcome.

Methods: 113 patients were identified (41 TKR, 37 UKR and 35 PFJR). All patients had mental health assessed preoperatively using SF-12. From the 12 questions a mental and a physical summary score can be calculated (MCS and PCS). The reduced WOMAC score was used pre-operatively to assess knee function and symptoms and then recorded at 8 and 24 months post-operation to assess outcome.

Results: 54% of the patients had pre-operative psychological distress. There was no statistically significant difference demonstrated between them mean MCS scores between the three operation groups. Pre-operative MCS had a significant effect such that increasing psychological distress lead to a worse twenty-four month outcome (p = 0.016). The effect of MCS is most marked in postoperative pain levels (p = 0.008) compared to function (p = 0.016). The mean 24-month rWOMAC in the severely distressed group (MCS< 40) was 28.4 compared to 17.4 in the psychologically well group (MCS> 60).

Conclusions: Pre-operative mental function prior to knee arthroplasty may provide useful information to guide patients as to their expected outcome in the consent process. Those patients with a very high mental component may be counseled to that although their distress is likely to improve with surgery, their eventual outcome may be worse. The effect of MCS may however only be clinically relevant in those patients with severe mental symptoms.

Sutures from intraosseous anchors are used to secure soft tissue down onto bone during healing. Increasingly anchors are made from absorbable materials. Poly lactide carbonate (PLC - poly lactide with calcium carbonate) is an absorbable formulation with osteoconductive properties that should enhance both tissue healing and its own replacement by bone over time. An animal model of soft-tissue-to-bone healing was used to assess the efficacy of PLC Bioraptor™ anchors in comparison to anchors of non-osteoconductive poly lactide (PLLA).

Forty-seven ewes were used in two groups of PLC or PLLA anchors, surviving to either four or 12 weeks. The patellar tendon was pared off the tibia, the footprint decorticated then the tendon re-attached. An external fixator protected the tendon from load bearing for three weeks. At post mortem the patella/patellar tendon/tibia complex was either prepared for histological examination or stored deep frozen for later measurement of peak load at failure.

Non-operated specimens failed within the tendon mid substance; the failure site of healing specimens was dependent on their strength, with the weakest through interpositional granulation tissue, stronger specimens through fibres at various distances from the bone and the strongest, by partial bone avulsion.

Active healing of the enthesis consisted of merging regions of

a) re-established cortical bone plate;

Healing tissues held by PLC suture anchors, were significantly stronger by 12 weeks than those held by PLLA anchors, possibly due to the calcium carbonate in the PLC anchor. However, the macroscopic and microscopic appearances of the healing tissues seemed little different between the two groups. This study indicates that PLC is a suitable replacement for PLLA in the fabrication of suture anchors. As well as its ability to produce stronger healing tissues, PLC has a shorter longevity in vivo and longer term is replaced by bone.

Hip and knee replacements are common and successful surgeries in orthopaedics. One of the known complications is fat embolism. Cemented implants used in arthroplasty allow good implant fixation and excellent long term results. However this has been associated with an increased incidence of fat embolism.

This experimental animal study compared the amount of fat embolism following three different surgeries in 30 Sprague Dawley rats. These surgeries simulated hip replacement procedures and included a control surgery, an un-cemented implant and a cemented implant. These animals were then sacrificed at 24 hours. All the lungs were fixed in formalin and then stained using Osmium Tetroxide. The amount of fat was then counted using a light microscope at 40x power.

Both the uncemented implant group (p < 0.001) and the cemented implant groups (p < 0.003) had significantly higher fat emboli from the surgical control group. There were also a significantly higher number of emboli (p < 0.05) in the cemented implant group compared to the uncemented implant group.

We conclude that fat embolism occurs in both the un-cemented and cemented hip replacement. The amount of emboli created by un-cemented hip replacement is less than the cemented hip replacement. The cement itself does not cause the complication of fat embolism. It is the high intramedullary pressure associated with the insertion of the implant, and the cementing process, that contributes to fat embolism. Devices or surgery that minimise this rise in pressure could reduce the amount of fat embolism.

The use of arthroplasty registers was initiated by Sweden in 1979. The practice has been adopted globally as best practice for recording the outcome of joint replacement surgery and for identifying early problems. The Trent and Wales Arthroplasty Audit Group began in 1990 and have recently produced outcome results. We have analysed the short-term outcomes of arthroplasty procedures at a DGH in order to assess comparability to this “gold-standard”.

In 2004, 231 primary arthroplasties were performed, by the two senior authors, at Musgrove Park Hospital (149 THR, 82 TKR). There was an overall complication rate of 8.7%. There was 1 periprosthetic infection in a THR that required revision (0.043%). 9 patients developed wound complications, principally superficial infections and haematoma formation. 2 patients, both THR developed, thromboembolic complications, one DVT and one pulmonary embolus. There was one periprosthetic fracture around a THR. The dislocation rate for THR was 3.35% (5/149). 3 of these were performed through a posterior approach and 2 through an anterolateral. 3 have required revision surgery.

We have demonstrated comparable results following joint arthroplasty to published teaching hospital series. We have shown that adequate infrastructure can exist in smaller units to accurately record outcome data following arthroplasty surgery.

Introduction Vertebroplasty (VP), where vertebral bodies are injected with polymethylmethacrylate (PMMA) cement, is used to treat various spinal lesions. More recently VP has been used for augmenting osteoporotic vertebral bodies that have fractured or are at risk of fracture. Although the complication rate for VP is low, thermal damage caused by the exothermic curing of PMMA has been implicated.

The aim of this series of experiments was to measure the temperatures reached during VP using a sheep model. The cement volume effect and inter cement differences were assessed. Spinal cord monitoring was undertaken to monitor spinal cord function during this procedure to validate this for clinical use.

Methods In the in vivo experiment each of the lumbar vertebral bodies of 10 sheep were injected with one of two cements (Simplex & Vertebroplastic) and one of two volumes (3.0ml or 6.0ml). This was undertaken through an open approach in the lumbar vertebrae. While performing the in vivo experimental studies 6 of the sheep were concurrently monitored using epidural Motor Evoked Potentials (MEP’s).

Results There was a significant increase in the temperature at the bone cement interface. The mean peak temperature at the bone-cement interface was 49.5 C (3.0ml Simplex); 61.47 C (6.0ml Simplex); 42.1 C (DePuy 3ml) and 47.2 (DePuy 6ml).

Spinal cord monitoring showed that when PMMA was injected into the correct location within the vertebral body there was no change in amplitude of the evoked potentials. When significant leakage of PMMA occurred, there was a decrease in amplitude of MEP’s.

Discussion In this sheep model, using cement volumes similar to those used in human clinical practice, we were able to monitor temperature changes within the vertebral body at the bone cement interface. The temperature of the bone cement interface reached temperatures that are known to cause tissue necrosis.

Using epidural monitoring we were able to show that when PMMA is injected into the correct location within the vertebral body there is no change in amplitude of MEP’s.

Percutaneous vertebroplasty (PVP), where vertebral bodies are injected with polymethylmethacrylate (PMMA) cement, is used to treat various spinal lesions. Although the complication rate for PVP is low, thermal damage caused by the exothermic curing of PMMA has been implicated.

This study was to measure the temperatures reached during PVP as PMMA cures as well as assessing the cement volume effect and inter cement differences. Validating spinal cord monitoring during PVP was also undertaken.

In the in vivo experiment each of the lumbar vertebral bodies of 10 sheep were injected with one of two cements and one of two volumes. Thermocouple monitoring was undertaken at the bone cement interface. While undertaking the in vivo experimental studies 6 sheep underwent epidural monitoring using Motor Evoked Potentials (MEPs).

The mean peak temperature at the bone-cement interface was 49.5 C (3.0ml Simplex); 61.47 C (6.0ml Simplex); 42.1 C (DePuy 3ml) and 47.2 (DePuy 6ml). Spinal cord monitoring showed that when cement was injected into the correct location within the trabeculae of the vertebral body no change in amplitude monitoring was noted. When leakage occurred, deliberate or unintended, amplitude changes were noted.

Using cement volumes similar to those used in human clinical practice in a sheep model we were able to monitor temperature changes. The temperature of the bone cement interface reached temperatures that are known to cause tissue necrosis. Using epidural monitoring we were able to detect leakage of cement during injection.

There is no general consensus amongst Orthopaedic Surgeons on how best to manage the urinary tract and its complications after lower limb arthroplasty. This prospective audit investigates whether post-operative urinary retention can be predicted pre-operatively using the validated International Prostate Symptom severity score (IPSS).

182 patients undergoing lower limb arthroplasty under spinal anaesthetic were given the IPSS questionnaire to complete pre-operatively and an audit into numbers catheterised post-operatively carried out.

69% of males and 39% of females required catheterisation. Following logistic regression analysis there was 0.85 predicted probability that males over seventy years would require catheterisation. The IPSS score was not useful in predicting retention in either sex at any age.

We propose that all males over seventy years undergoing this type of surgery should be catheterised pre-operatively and all other patients should be catheterised post-operatively with close monitoring of bladder volumes to prevent established urinary retention.

Introduction The Constant-Murley Score is the functional score currently recommended by the British Shoulder and Elbow Society and by the European Society for Surgery of the Shoulder and Elbow. Normal Values for shoulder assessment are imperative for the diagnosis of pathology and measurement of treatment outcome. Normal values for the UK are currently not known. Several techniques have been described for the assessment for strength and measurement of this paraemeter differs between published series.

Patients and method 122 patients over 50 (62 male) attended a GP surgery for a Constant Score measurement. Constant Score was assessed using three techniques for strength measurement: maximum strength with myometer (Mmax), mean strength with myometer (Mmean) and maximum strength with fixed spring balance (FSB).

Results Maximum strength values measured by myometer or fixed spring balance were very similar with a mean difference of 0.5 (less than the calibration of a spring balance). Mean strength measurements were consistently lower than maximum strength measurements with a mean difference of 3 points. Age and sex both significantly affected Constant Score (P< 0.001, P< 0.001). Constant Score falls by 0.4 points per year over 50. Males have a score 8 points greater than females.

Conclusions Constant Score decreases predictably with age in the UK. Methods of strength assessment are not the same. A uniform method of shoulder strength assessment or correction for method is required to allow meaningful comparisons between series.

Introduction: Vertebroplasty (VP) is a relatively new procedure to treat osteoporotic compression fractures of vertebral bodies. During this procedure polymethyl-methacrylate (PMMA) is injected into vertebral bodies. However there is the concern, that fat embolism (FE) and acute hypotension could occur as in a variety of other orthopaedic procedures.

Aim: To investigate whether FE and acute hypotension are potential complications of VP using an animal model.

Methods: In six sheep, 6.0 ml PMMA were injected unilaterally into the L1 vertebral body. Transœsophageal echocardiography was used to monitor the pulmonary artery for bone marrow and fat particles until 30 minutes post-operatively. Pulse, arterial and venous pressures were also recorded. The lumbar spine and the lungs were harvested post mortem. The histopathologic score, (percentage of lung fields occupied by intravascular fat globules as seen through the microscope), was calculated.

Results: The first showers of echogenic material were visible approximately seven seconds after the beginning of the cement injection and lasted for about 2.5 minutes. The injection of bone cement caused a very rapid decrease in the heart rate after two seconds followed by a fall in the mean arterial pressure after 6.0 seconds. A maximum fall in heart rate was accompanied by a delayed fall in mean arterial pressure of 33.0 mmHg (P=0.0003) at 36seconds. The heat rate had returned to the baseline by 89 seconds and had increased by 10 beats/min (P=0.02) at 25 minutes. Mean arterial pressure had recovered by 209 seconds and was not different from the baseline at 25 minutes. Post mortem examination showed that no leakage of cement into the spinal cord had occurred. The histology revealed fat globules and bone marrow cells in the smaller and larger vessels throughout the lungs. The histopathologic score was 5.2 ± 0.9%.

Conclusions: This study clearly showed that VP resulted in FE with a two-phase decrease in heart rate and arterial blood pressure. The first phase was probably due to an autonomic reflex and the second phase was due to the passage of fat emboli through the right heart and obstructing the lungs.

Introduction: After more than 10 years of clinical experience, hydroxyapatite (HA) coated orthopaedic implants are now an established, viable alternative to porous coatings for achieving good implant fixation. However, developments are continuing to improve the nature and adhesion of the HA coating.

Aim: To investigate the biological attachment characteristics of titanium and highly crystalline HA implant coatings in the metaphysis of an animal model.

Method: Titanium alloy implants with a coating of commercially pure titanium (Ti) or highly crystalline HA were evaluated by light microscopy and pullout tests after one, two and four weeks of unloaded implantation in the tibial and femoral metaphyses of 18 sheep.

Results: The interface shear strength pullout increased from approximately 29N/cm2 at one week to approximately 326N/cm² at two weeks. At four weeks the pull-out strength for Ti and HA coated implants was 1,004.87 ± 189.82N/cm2 and 1,043.26 ± 260.61N/cm2 respectively. The pullout strength increased significantly over time up to four weeks, but the difference between the coatings was not statistically significant at any time interval.

Histomorphometric analysis showed an increase of bone-implant contact between one and two weeks from 0 to 15% for Ti and 0 to 20% for HA coated implants. At four weeks Ti and HA implants showed 44% and 60% bone-implant contact respectively. There was a significant increase in bone-implant contact over time for both coatings. HA implants had significantly higher bone-implant contact at two and four weeks. Light microscopy revealed that bone grew into HA coated surfaces in the form of feet, spreading over the surface. Whereas for Ti the newly formed bone looked like a bridge linking the original bone with the implant surface.

Conclusion: The different growth patterns of bone into Ti and HA surfaces resulted in different bone-implant contact areas. Highly crystalline hydroxyapatite coatings enhanced the osseointegration in the early stages of bone healing. However there was a discrepancy between the mechanical and histological results. This may suggest that the mechanical failure does not occur at the implant-bone interface.

Introduction: The surface of articular cartilage is adapted to low-friction movement. It is important for lubrication, resists shear and compression, and allows transfer of fluid, nutrients and metabolites between synovial fluid, matrix and cells. Surface damage is common following trauma and in early osteoarthritis. The use of intra-articular hyaluronan (visco-supplementation), or oral glucosamine and chondroitin, is claimed to enhance surface protection and/or repair. To validate such treatment biologically, a better understanding of normal structure and function of the cartilage surface is required.

Methods: The surface of femoral condylar cartilage of sheep was examined using transmission electron microscopy (TEM), scanning electron microscopy and polarising microscopy. Fresh specimens were obtained before and after wiping the surface with lens tissue.

Results: TEM of un-wiped normal cartilage showed a thin surface coating of amorphous electron-dense material containing occasional microvesicles and bundles of detaching collagen fibrils. In wiped cartilage this coating was absent, suggesting the superficial layer described in previous studies (lamina splendens of MacConaill), is an adherent coating, probably aggregated proteoglycan, hyaluronate and matrix degradation products. The definitive cartilage surface was a smooth network of fine collagen fibres supported by a mesh of collagen containing microvesicles and particles. More deeply a denser layer of collagen ran parallel to the joint surface. The most superficial zone would allow rapid surface exchange of fluid and particles while the deeper collagen would protect the underlying cells and limit fluid moving deeper during joint loading.

Conclusions: The findings have implications for therapy aimed at cartilage surface protection and/or repair.

Introduction: Vertebroplasty (VP) is a new prophylactic treatment for preventing osteoporotic compression fractures of vertebral bodies. During this procedure polymethylmethacrylate (PMMA) is injected into several vertebral bodies. It has been shown that fat embolism (FE) with acute cardiopulmonary deterioration occurs during VP as it does in a variety of other orthopaedic procedures (e.g. knee and hip replacements).

Aim: To investigate the cardiovascular changes during FE caused by multiple VP using an animal model.

Method: PMMA was injected unilaterally, into L1 – L6 in six sheep, with 10 minutes between injections. Arterial, venous and pulmonary arterial pressure, cardiac output and blood gas values were recorded before injection and again after the injection at one, three, five and 10 minutes. The lungs were harvested post mortem and the histopathologic score (percentage of lung fields occupied by intravascular fat globules as the field of the microscope) was calculated.

Results: The sequential injection of bone cement into six vertebral bodies from values before injection of L1 to 10 minutes after injection of L6 resulted in significant falls in arterial blood pressure (P< 0.0001), cardiac output (P=0.0049), pO² (P< 0.0001) and pH (P< 0.0001). There were also significant rises in pulmonary arterial pressure (P=0.0005) and pCO2 (P< 0.0001), but no significant change in central venous pressure. The histopathological score was 19.1±1.94%,

Conclusions: This study clearly showed that multiple VP in sheep leads to FE with major cardiovascular reactions. Arterial blood pressure showed a stepwise, cumulative fall and was clearly the best parameter to demonstrate these reactions. This suggests that in human patients, particular attention should be paid to falls in arterial blood pressure during multiple VP.

Vertebroplasty (VP) is a new prophylactic treatment for preventing osteoporotic compression fractures of vertebral bodies. During this procedure polymethylmethacrylate (PMMA) is injected into several vertebral bodies. However, there is the concern, that fat embolism (FE) and acute hypotension could occur as in a variety of other orthopaedic procedures.

This study was undertaken to investigate whether FE and acute hypotension are potential complications of VP using an animal model.

In six sheep 6.0 ml PMMA were injected unilaterally into L1. Transesophageal echocardiography was used to monitor the pulmonary artery for bone marrow and fat particles until 30 minutes postoperatively. Pulse, arterial and venous pressure were also recorded. Post mortem the lumbar spine and the lungs were harvested. The lungs were subjected to histological evaluation.

The first showers of echogenic material were visible approximately 7.0 seconds after the beginning of the cement injection and lasted for about 2.5 minutes.

Injection of bone cement elicited a very rapid decrease in heart rate after 2.0 seconds followed by a fall in mean arterial pressure after 6.0 seconds. A maximum fall in heart rate was accompanied by a delayed fall in mean arterial pressure of 33.0 mmHg (P=0.0003) at 36.0 seconds. Heat rate had returned to baseline by 89.0 seconds and had increased by 10.0 beats/min (P=0.02) at 25 minutes. Mean arterial pressure had recovered by 209.0 seconds and was not different to the baseline at 25 minutes.

The post mortem inspection revealed disseminated haemorrhages on the lung surface and throughout the parenchyma mainly in the caudal lobes of all six animals. No leakage of cement into the spinal cord was detected. In histology fat globules and bone marrow cells were observed in both the smaller and larger vessels throughout the lung.

This study clearly shows that VP resulted in a two-phase decrease in heart rate and arterial blood pressure. The first phase was probably due to an autonomic reflex and the second phase was due to the passage of fat emboli through the right heart and obstructing the lungs.

A method is described which produces an isolated Grade II injury in the medial collateral ligament of the sheep's knee. The untreated injury was followed in 32 animals for up to six weeks. Histology revealed progressive healing of the lesions by a cellular response mediated by fibrocytes rather than by the classically described inflammatory response. Mechanical testing showed that the tensile strength of the ligament was initially reduced to 13% of normal but that strength and compliance were regained after six weeks.