This study documents the gross and histologic structure of the infrapatellar plica, and fat pad, and adds to an earlier report to the COA. The important new findings are that the femoral attachment of the plica is an enthesis, and that the plica itself is.

This study seeks to demonstrate that the structure of the fat pad (FP) and infrapatellar plica (IPP) is that of an enthesis organ.

Twelve fresh frozen cadaver knees, each with an IPP, were dissected and the gross anatomic features recorded. The IPP and FP were harvested for study. Representative histologic sections were prepared on tissue fixed in 10% neutral buffered formalin, embedded in paraffin, cut at 4 microns on a rotatory microtome. Staining techniques included hematoxylin and eosin, Masson's trichrome, elastic stain and S100. Appropriate decalcification of sections of the femoral insertion of the IPP was performed. All sections were examined by light microscopy at low, medium and high power. IPP types included 8 separate, 1 split, 2 fenestrated, and one vertical septum. The origin of the IPP is a fibrous arc arising from the apex of the notch separate from the margin of the articular cartilage. This attachment site is the instant centreof rotation of the IPP and FP; they are thus not isometric. The central zone of the IPP consists of a mix of connective tissue types.

Representative sections taken of the femoral attachment of the IPP display a transition zone between dense fibrillar collagen of the IPP, then fibrocartilage and cortical bone similar to a ligament attachment site or enthesis. The central plica histology is composed predominantly of dense regular connective tissue with variable clear space between the collagen bundles, and is thus ligamentous. There is abundant elastase staining throughout, as well as crimping of the collagen suggesting capacity for stretch. S100 staining demonstrates nerves around and in the substance of the IPP. The central body shows lobulated collections of mature adipose tissue admixed with loose connective tissue, containing abundant small peripheral nerves and vessels (all showing crimping and redundancy), merging with the dense fibrous tissue of the IPP. The FP is highly innervated, deformable, and fibro-fatty. Its histology shows lobules of fat, separated by connective tissue septa, which merge with the synovial areolar membrane surrounding the FP.

The linked structures, IPP, central body, and FP occupy the anterior compartment, and function as an enthesis organ: the IPP tethers the FP via the central body and together they rotate around the femoral origin of the IPP. They are not isometric, and must stretch and relax with knee motion. The histology correlates with this requirement. The origin of the IPP is an enthesis, a new observation. Elastase staining, redundancy of vessels and nerves, crimping and redundancy of the dense connective tissue all reflect the requirement to deform. The fat pad merges with the central body, both highly innervated space fillers, tethered by the IPP, which is a non-isometric ligament, also containing nerves. The important clinical significance of these structures is that release of the IPP at the origin reuces or eliminates anterior knee pain in most.

INTRODUCTION

Immediate post-operative stability of a cementless hip design is one of the key factors for osseointegration and therefore long-term success [1]. This study compared the initial stability of a novel, shortened, hip stem to a predicate standard tapered wedge stem design with good, long-term, clinical history. The novel stem is a shortened, flat tapered wedge stem design with a shape that was based on a bone morphology study of 556 CT scans to better fit a wide array of bone types [2].

Purpose

Anterior knee pain has been relieved by resection of the infrapatellar plica (IPP). The question is: How? The hypothesis is: the IPP acts as an intra-articular ligament, a mechanical link between the forces of knee motion, the fat pad (FP) and the distal femur, holding the FP captive through the arc of motion. Release of the IPP severs this link, allowing the highly innervated FP to move freely. This may allow any underlying pathologic process to heal.

Purpose: To review the existing practice of coding in spinal surgery and ascertain its accuracy for surgical procedures, co-morbidities and complications.

Methods: A retrospective review of 70 cervical and 100 lumbar consecutive spinal surgeries performed since April 2006 was conducted. The clinical coding data and hospital notes were reviewed.

Results: Coding data of 5 cervical spine surgeries were not available. Of the 165 cases, the accuracy of primary procedural codes was 93.9% (90.8% cervical & 96% lumbar). This reduced to 77.6% (75.4% cervical & 79% lumbar) when the accuracy for entire description of performed surgery was considered. Medical co-morbidities were coded appropriately in 64.2% of the patients (55% cervical & 70% lumbar). The procedural codes did not specifically reflect the surgery performed and lacked reproducibility. Surgical levels were coded incorrectly in 9% of the cases. Cervical surgeries were coded as lumbar in 4 and posterior surgery as anterior in 3 cases respectively. The commonly missed co-morbidities were drug allergies, hypercholesterolemia, smoking and alcoholism. Post-op adverse events were coded in 75% of the cases (16/20 cervical & 5/8 lumbar). The accuracy was better for lumbar as compared to cervical spinal surgeries.

Conclusion: Coding is a universal language of communication and its accuracy is important not just for PbR, but for data quality, audit and research purposes too. The financial implications regarding PbR governed by HRG codes (dictated by OPCS 4.4 & ICD–10 codes) are discussed. Following this study, a clinical coding facilitation form has been introduced to improve data quality.

Ethics approval: None

Interest statement: None

Introduction: Accurate & ethical coding is challenging and directly impacts on Payment by Results (PbR). The objectives were to review the existing pattern of coding for lumbar spinal surgery and ascertain its appropriateness & accuracy for surgical procedures, medical comorbidities and post-op complications.

Methods: A retrospective review of 100 consecutive lumbar spine surgeries operated from Apr2006–Jan2007 was conducted. The coding excel sheet, hospital notes and laboratory reports were reviewed.

Results: The primary procedural accuracy was 96%, however this reduced to 79% for the entire description of performed surgery. The procedural codes did not specifically reflect the surgery performed and lacked reproducibility. Spinal fusion codes were omitted and revision cases were coded as primary surgeries in 2 instances each. Surgical levels were coded incorrectly in 12 and harvest of iliac crest bone graft omitted in 4 cases respectively. Medical comorbidities were coded appropriately in 70%. The commonly missed comorbidities were drug allergies, hypercholesterolemia, smoking and alcoholism. Post-op adverse events were coded in 62.5% of the cases(5/8).

Conclusion: Coding is a universal language of communication amongst healthcare professionals. Its accuracy is important not just for PbR, but also for data quality, audit and research. The financial implications regarding PbR governed by Healthcare Resource Group (HRG) codes (dictated by Official population and census surveys [OPCS4.4] & International classification of diseases [ICD–10] codes) are discussed. The awareness of clinical coding is low amongst junior doctors. Literature emphasises qualification of coders, legible documentation by physicians and interaction between coders & clinicians.

Introduction: Accurate and ethical coding is challenging and directly impacts on Payment by Results (PbR). The aims & objectives of this study were to review the existing pattern of coding for spinal surgery and ascertain its appropriateness & accuracy for surgical procedures, medical co-morbidities and post-op complications.

Methods: A retrospective review of 70 consecutive cervical and 100 consecutive lumbar spine patients who were operated from April 2006 onwards was conducted. The excel sheet provided by coding department, hospital notes – clinic letters, physicians’ entries, theatre notes and laboratory reports (biochemistry/microbiology/histology) – were reviewed. Of the 170 cases, 165 were available for analysis.

Results: Coding data of 5 patients who underwent cervical spine surgeries were not available. Of the 165 cases, the accuracy of primary procedural codes was 93.9% (90.8% cervical & 96% lumbar). However this reduced to 77.6% (75.4% cervical & 79% lumbar) when the accuracy for entire description of performed surgery was considered. The procedural codes did not specifically reflect the surgery performed and lacked reproducibility. Surgical levels were coded incorrectly in 9% of the cases. Cervical surgeries were coded as lumbar in 4 and posterior surgery as anterior in 3 cases respectively. Harvest of iliac crest bone graft was not coded in 5 cases. Medical comorbidities were coded appropriately in 64.2% of the patients (55% cervical & 70% lumbar). The commonly missed comorbidities were drug allergies, hypercholesterolemia, smoking and alcoholism. Post-op adverse events were coded in 75% of the cases (16/20 cervical & 5/8 lumbar). The accuracy was better for lumbar as compared to cervical spinal surgeries.

Conclusion: Coding is a universal language of communication amongst healthcare professionals. Its accuracy is important not just for PbR, but for data quality, audit and research purposes too. The financial implications regarding PbR governed by HRG codes (dictated by OPCS 4.4 & ICD–10 codes) are discussed. The awareness of clinical coding is low amongst junior doctors. Following this study, a clinical coding facilitation form has been introduced to improve data quality. Our plan is to close the audit loop and re-evaluate. Literature emphasises qualification of coders, legible documentation by physicians and interaction between coders and clinicians.

The role of vacuum mixing on the reduction of porosity and on the clinical performance of cemented total hip replacements remains uncertain. We have used paired femoral constructs prepared with either hand-mixed or vacuum-mixed cement in a cadaver model which simulated intra-operative conditions during cementing of the femoral component. After the cement had cured, the distribution of its porosity was determined, as was the strength of the cement-stem and cement-bone interfaces.

The overall fraction of the pore area was similar for both hand-mixed and vacuum-mixed cement (hand 6%; vacuum 5.7%; paired t-test, p = 0.187). The linear pore fractions at the interfaces were also similar for the two techniques. The pore number-density was much higher for the hand-mixed cement (paired t-test, p = 0.0013). The strength of the cement-stem interface was greater with the hand-mixed cement (paired t-test, p = 0.0005), while the strength of the cement-bone interface was not affected by the conditions of mixing (paired t-test, p = 0.275). The reduction in porosity with vacuum mixing did not affect the porosity of the mantle, but the distribution of the porosity can be affected by the technique of mixing used.

There is little information available regarding mechanical aspects of cemented implant loosening and the initiation and development of cement damage. Previous studies have come to a variety of conclusions about the development of cement damage and the relative importance of voids, the stem/cement interface and the cement/bone interface.

Cement micro-cracks and stem/bone micro-motions were quantified for Charnley Cobra stems under “stair-climbing” loads. Six stem/cement/femur constructs were subjected to loads based on estimated body weight for 300 kcycles at 2 Hz; two additional constructs were not loaded. Transverse sections were cut at 10 mm intervals, stained with a fluorescent dye penetrant and examined using epifluorescence stereo-microscopy.

Despite the aggressive loading, all stem/bone micro-motions were small and all stems were “well fixed” at the end of the loading. The only consistent micro-motion was internal rotation but this did not significantly correlate with cement damage (p=0.9). For cyclically loaded constructs mean crack length was 0.49 mm (SD 0.37, range 0.07 to 4.42) and for non-loaded controls mean crack length was 0.25 mm (SD 0.18, range 0.03 to 1.16). Total crack length (46–281 mm) was significantly correlated (R2=0.819, p=0.002) with femoral head load (0 & 1.0–1.8 kN). There was a significantly (p< 0.05) greater proportion of damage at the cement/bone interface (66% ± 9) than at the stem/cement interface (28% ± 8). A small fraction of micro-cracks involved voids (5% ± 5), but these were significantly (p< 0.001) less than the cement/ bone fraction. Micro-cracks in unloaded specimens were evenly distributed axially (R2=0.0002, p=0.95) consistent with the theory that they were induced by cement shrinkage. ANCOVA for total crack density using head load and axial position as covariates showed a significant positive effect for head load (p< 0.0001) and a significant interaction between head load and axial position (p=0.001); under load, micro-crack density increased proximally, and this effect was stronger with increasing head load.

Highly polished femoral stems with a double taper have had outstanding long-term clinical results. Recently a stem with a third, cross-sectional taper was introduced with the goal of providing additional stability while still utilising the polished taper concept.

The goal of the present study was to determine if there were differences in the mechanical stability and cement damage due to cyclic loading of a triple-tapered (C-stem, J& J-DePuy) and a double-tapered design (TPS, J& J-DePuy). Six pairs of cadaveric femurs were cemented with either C-stem or TPS stems using contemporary techniques. Specimens were cyclically loaded using a stair-climbing apparatus with femoral head and abductor loads for 1 000 to 266 000 loading cycles. Motion between the stem and bone was measured using a 6 dof measurement system. Following testing, specimens were sectioned at four transverse levels and the number and length of cracks in the cement were measured.

All stems were extremely well fixed after loading. The C-stem did not subside during loading except for one outlier that was cemented ‘high’. The TPS stem had a pattern of rapid subsidence over the first 100 cycles (mean 0.032 mm) followed by a more gradual subsidence (0.05 mm at 266 k cycles). ANCOVA showed that the TPS-stems rotated significantly more than the C-stems (p< 0.0001), that the rotation of both stems increased with number of loading cycles (p=0.022) and that the effect of number of loading cycles was greater for the TPS stems (p=0.047). Total crack length was not a function of number of loading cycles, nor was it different for the two stem designs (p=0.33).

The outlier C-stem had micromotion behavior similar to the TPS stem. The reason for this is unclear, but could be due to reduced lateral-proximal cement. Thus it is possible that both the stem cross-sectional and in-plane shape contribute to the stability of the C-stem design.

Bone-cement shrinkage has never been quantified in a stem/cement/femur construct. We observed gaps around femoral stems in transverse sections of stem/cement/femur constructs; a greater proportion of stem/cement (s/c) interface gaps were found around grit blasted sections of stems than satin finished sections. If s/c gap formation were a shrinkage artifact then mantles with few s/c interface gaps must manifest shrinkage elsewhere, at the c/b interface or voids. ‘Mould-gaps’ at a c/b interface have been described previously but not quantified. We analysed the area of gaps at both interfaces. We hypothesised 1) Total gap area was the same for all transverse sections. 2) Satin sections had greater c/b gap areas than grit sections.

Transverse sections of stem/cement/femur constructs were processed to highlight gap areas. Five stems had a satin finish (Ra 0.75 um) and five were proximally grit-blasted (Ra 5.3 um). Sections were coated with matt black spray paint and then polished with emery paper. This process left all interface gaps and voids filled with black paint, which facilitated digital imaging. Gaps were visually identified and measured using Image-Pro. Gap areas for each transverse section were normalised by the area of cement in that section.

Gaps were not evenly distributed; there was obvious localisation at both interfaces. No significant difference found between surface finishes in total gap area ((satin 3.1% ± 1.4):(grit 3.4% ± 1.5)), supporting our first hypothesis. S/c gap areas were significantly greater around grit blasted sections ((satin 0.1% ± 0.4):(grit 1.9% ± 1.7) p< 0.0001). C/b gap areas were significantly greater around satin finished sections ((satin 2.3% ± 1.3):(grit 1.0% ± 0.9) p< 0.0001), supporting our second hypothesis.

Shrinkage can localise into large interface gaps; which must lead to stress concentrations. C/b gaps are potentially benign as they can fill with bone. Cement failure at points of s/c contact would generate debris hindering bone formation.

We have compared the interface morphology at the stem-cement interface of standard Charnley stems with a satin finish (Ra = 0.75 μm) with identical stems which had been grit-blasted over their proximal third (Ra = 5.3 μm) to promote a proximal bond. The stems were cemented into cadaver femora using conventional contemporary cementing techniques. After transverse sectioning, we determined the percentage of the perimeter of the stem which had a gap at the interface.

There were substantial gaps (mean 31.4 ± 17.1%) at the stem-cement interface in the grit-blasted region. This fraction was significantly (paired t-test, p = 0.0054) higher than that found around the contralateral satin-finished stems (mean 7.7 ± 11.7%). Although studies of isolated metal-cement interfaces have shown that the bond strength can increase with surface roughness it cannot be assumed that this effect will be observed under clinical conditions.

We compared the ability of three different posterior cruciate ligament (PCL) reconstructions to restore normal anteroposterior laxity to the knee from 0 to 130° of knee flexion.

Cadaver knees were tested intact, after PCL rupture or after bone-patellar tendon-bone grafting. Grafts were performed isometrically or with a single bundle representing the anatomical anterior PCL fibre bulk (aPC) or with a double bundle that added the posterior PCL fibre bulk (pPC). The grafts were tensioned to restore normal knee laxity at 60° of flexion, except for the pPC which was tensioned at 130°.

The isometric graft led to overconstraint as the knee extended resulting in high graft tension in extension and excess laxity in flexion. The aPC graft matched normal laxity from 0 to 60° of flexion but was lax from 90 to 130° of flexion. Only the double-bundled graft could restore normal knee laxity across the full range of flexion.