Prevention of thermal tissue injury induced by the application of polymethylmethacrylate to the calvarium

Gender Affirming Facial Surgery-Anatomy and Procedures for Facial Masculinization

For some patients, feminine facial features may cause significant gender dysphoria. Multiple nonsurgical and surgical techniques exist to masculinize facial features. Nonsurgical techniques include testosterone supplementation and dermal fillers. Surgical techniques include soft tissue manipulation, synthetic implants, regenerative scaffolding, or bony reconstruction. Many techniques are derived from experience with cisgender patients, but are adapted with special considerations to differing anatomy between cisgender and transgender men and women. Currently, facial masculinization is less commonly sought than feminization, but demand is likely to increase as techniques are refined and made available.

Accuracy of patient-specific temporal implants using PEKK

The main aim of this study was to evaluate the accuracy of immediate CAD/CAM reconstruction of the temporal hollowing following temporalis muscle surgery, using a patient-specific implant (PSI) PEKK model. This case series included ten patients who underwent maxillofacial reconstruction using temporalis muscle flap (TMF). The study involved the preoperative planning and fabrication of the temporal implant using virtual surgical planning software. The planning was based on multislice CT scans, from which DICOM files were used to fabricate a 3D model of the temporalis muscle using polyetherketoneketone (PEKK). The patients were followed up for 12 months, to check for any signs of infection or mobilization, and to assess accuracy. At the end of the follow-up period, all the patients showed acceptance of the external appearance, with no signs of infection or rejection. These customized implants were measured and compared with their original 3D preoperative planning using a point-based analysis. This revealed a mean difference (±SD) of 0.0373 (±0.3036) mm and a median difference (Q1 to Q3) of 0.0809 (-0.2108 to 0.2769) mm. The study demonstrated that a highly accurate duplication of PSIs can be achieved using this template-molding workflow. The use of PEKK PSIs resulted in uneventful healing and esthetic acceptance by the patients and, therefore, is a relevant treatment option when temporal hollowing has to be corrected.

Integrated Forehead and Temporal Augmentation Using 3D Printing-Assisted Methyl Methacrylate Implants

BACKGROUND

Achieving aesthetic results with forehead augmentation procedures remains challenging. We have developed a method of integrated forehead and temporal augmentation using a three-dimensional (3D) printing-assisted methyl methacrylate implant.

OBJECTIVES

The study objective was to assess the importance of combined temporal augmentation when performing forehead augmentation.

METHODS

We identified 34 patients (from 2000 to 2010) who underwent forehead augmentation with a methyl methacrylate implant contoured in situ during surgery and 41 patients (from 2010 to 2016) who underwent integrated forehead and temporal augmentation with a prefabricated methyl methacrylate implant. We conducted a retrospective chart review of patient data including operation time, complications, and instances of revision surgery. Two blinded plastic surgeons scored the aesthetic results of the operations on a 4-point scale (1, poor, to 4, excellent) based on preoperative and posttreatment photographs.

RESULTS

The integrated augmentation method resulted in a lower frequency of posttreatment implant removal (one [2%] vs. six [18%]; P < .05), a lower frequency of filler injection for touch up (one [2%] vs. six [18%]; P < .05), and higher mean aesthetic scores (3.7 ± 0.5 vs. 2.2 ± 1.0; P < . 001) compared to the forehead augmentation method. There was no statistically significant difference in surgical complications between the two groups.

CONCLUSIONS

Integrated forehead and temporal augmentation using a 3D printing-assisted methyl methacrylate implant may be the optimal available procedure, enabling the custom fabrication of contours requested by the patient and providing a rejuvenating and balancing effect on facial appearance.

LEVEL OF EVIDENCE 3

Patient-specific polymethylmethacrylate prostheses for secondary reconstruction of large calvarial defects: A retrospective feasibility study of a new intraoperative moulding device for cranioplasty

PURPOSE

The aim of this study was to review a new template-based technique for intraoperative patient-specific cranioplasty manufacturing (PSCM) with polymethylmethacrylate (PMMA) to cover large calvarial defects.

MATERIAL AND METHODS

A polypropylene foil thermoformed on a three-dimensional reprint of the calvarial defect was used as an intraoperative moulding device for PMMA between August 2012 and December 2015. Surgical and radiological data were retrospectively reviewed, and a patient questionnaire was used to assess functional and cosmetic outcome (numeric rating scale, Odom's criteria).

RESULTS

Seventeen patients (mean age 42.2 ± 14.5 years) received PSCM. Operating time averaged 130 ± 34 min, and the approximate blood loss was 293 ± 185 ml. Volumetric analysis revealed a lower implant volume compared to index bone (mean 66.5 vs. 72 cm³, p = 0.513), the mean difference in thickness being the lowest in the posterior parietal and pterional (0.4-0.7 mm) and the highest in the anterior-superior frontal area (1.8 mm). Cosmetic satisfaction averaged 9 ± 1.5, with 70.6% of patients judging the overall result as excellent or good and 29.4% as satisfactory. Mean follow-up was 19.5 ± 13.3 months, with an overall complication rate of 17.6%, including 11.8% surgical site infections (SSIs) and one implant removal.

CONCLUSIONS

Intraoperative PSCM using PMMA moulded on a thermoformed polypropylene foil leads to satisfactory outcomes. It is a safe technique with complication rates comparable but not superior to those of other alloplastic techniques, but the device has considerable production costs.

Alloplastic Augmentation of the Asian Face: A Review of 215 Patients

BACKGROUND

Asian aesthetic surgery has become increasingly popular over the last decade, especially augmentation of characteristically flattened facial features. Alloplastic implants are an option for facial augmentation, however many avoid their use due to concerns for morbidity associated with their use.

OBJECTIVES

To validate our hypothesis that when used properly, alloplastic implants have a low complication profile and provides excellent aesthetic results.

METHODS

A retrospective review was performed of all Asian patients undergoing alloplastic facial augmentation between 2009 and 2013 by a single surgeon. Procedures included augmentation of the forehead, nasal dorsum, midface, and chin. Charts were reviewed for outcomes including infection, extrusion, malposition, and operative revision.

RESULTS

Two hundred and fifteen patients had 243 implants placed. Of 141 nasal augmentations, there were 2 infections (1.4%), 1 extrusion (0.7%), 7 malpositions (4.9%), and 16 revisions (11.3%), 5 for malposition, 2 for contour irregularity, and 9 for aesthetic change. Augmentation genioplasty was performed in 40 patients with 1 malposition (2.5%) and 6 revisions (15%), 4 for under-correction and 2 for aesthetic change. Thirty-one midface and 31 forehead augmentations were performed without complications. One patient (3.2%) had forehead implant removal for aesthetic change. Overall infection and extrusion rates were 0.8% and 0.4%, respectively.

CONCLUSIONS

By utilizing surgical techniques such as creation of a precise sub-periosteal pocket, placing the implant away from the incision site, and leaving well-vascularized soft tissue coverage under minimal tension, alloplastic implants can safely be used as a first-line option for Asian facial augmentation.

LEVEL OF EVIDENCE

4 Therapeutic.

Bioactive-glass in Oral and Maxillofacial Surgery

The use of synthetic materials to repair craniofacial defects is increasing today and will increase further in the future. Because of the complexity of the anatomy in the head and neck region, reconstruction and augmentation of this area pose a challenge to the surgeon. This review discusses key facts and applications of traditional reconstruction bone substitutes, also offering comparative information. It then describes the properties and clinical applications of bioactive-glass (B-G) and its variants in oral and maxillofacial surgery, and provides clinical findings. The discussion of each compound includes a description of its composition and structure, the advantages and shortcomings of the material, and its current uses in the field of osteoplastic and reconstructive surgery. With a better understanding of the available alloplastic implants, the surgeon can make a more informed decision as to which implant would be most suitable in a particular patient.

Aesthetic occiput augmentation using methylmethacrylate

Cranioplasty for only aesthetic reasons has not been commonly performed to date. However, recently there has been a new focus by the public on a more aesthetically pleasing head shape with frequent patient requests for purely aesthetic contouring of the occiput, an important definer of cosmetic head shape. For example, in Asia, where the normal cranial shape is mesocephalic or brachycephalic and often with a planar occiput, requests for its aesthetic correction are increasingly common. Accordingly, the author developed a minimally invasive occiput augmentation using methylmethacrylate. In this study, the indications for aesthetic occiput contouring were planar occiput, left-right asymmetric occiput, and grooved occiput. Under local anesthesia, soft methylmethacrylate is subperiosteally inserted through a small incision (about 5-cm length), manually and precisely contoured in situ through the scalp to the desired occipital shape. All is performed as an outpatient procedure, and a quick recovery is the case. Between March 2007 and October 2013, 959 patients received such aesthetic occiput augmentation. The mean follow-up period was 49 months (range, 3-84 months). Nearly all patients were satisfied with the outcome, and complications were very rare. Only 5 patients (0.5%) needed additional corrective procedures. The author has concluded that aesthetic occiput augmentation using methylmethacrylate yields consistent, predictable, and satisfactory results. Additional long-term follow-up is required for a final conclusion, however.

In Situ Cranioplasty for Hyperostosing Meningiomas of the Cranial Vault

Objective:

Hyperostosis of the bone overlying meningiomas has been reported in up to 50% of cases. The skull becomes infiltrated by meningothelial tumor cells, necessitating removal of the hypertrophied bone to achieve a complete tumor resection. Unfortunately, aesthetic reconstruction of large bony defects can pose a significant challenge intra-operatively. Custom cranioplasty implants are very expensive and can only be fabricated after the bony defect exists, requiring a second surgery for implantation. Although numerous composite materials exist to repair the defects at the time of tumor resection, the challenge is to create an implant that fits appropriately without shifting and approximates the natural curvature of the skull. We have developed a technique for an “in situ cranioplasty” using a composite construct with strength in compression and tension.

Technique:

After the skull is reshaped by shaving down part of the hyperostotic bone, titanium mesh is molded to the surface of the skull and screwed into the surrounding normal bone. The bone flap is then removed by drilling a trough at the outer margin of the tumor-involved skull and removing a ring of normal surrounding bone. The central portion of tumor involved skull is then craniectomized. The mesh can be reapplied and the full thickness of the central bone can be reconstructed with polymethylmethacrylate, yielding a solid construct perfectly matched to the patient's natural head shape.

Conclusion:

This novel technique yields a sturdy, aesthetic, and cost-effective result which can be used to address any cranial vault defect at the time of tumor resection.

Metaphyseal bone formation induced by a new injectable β-TCP-based bone substitute: a controlled study in rabbits

PURPOSE

Adequate filling of bone defects still poses a challenge in every day clinical work. As many bone defects are irregularly shaped the need for appropriate scaffolds reaching the complete defect surface are great. The purpose of this pre-clinical pilot study was to investigate the handling, biocompatibility, biodegradation and osteoconductivity of a new pasty bone substitute (pure phase β-TCP, hyaluronic acid, methylcellulose) in bone tissue.

METHODS

In an unilateral tibial defect model the peri-implant and bone tissue response to the new pasty bone substitute was tested in New Zealand white rabbits for up to 24 weeks compared to empty controls. Analysis included HR-pQCT scans, histomorphometric evaluation and quantification of vascularization of un-decalcified histological slices.

RESULTS

After 1 week the experimental group presented significantly higher new bone volume fraction (p = 0.021) primarily consisting of immature bone matrix and higher vessel density compared to controls (p = 0.013). After 4 weeks bone formation was not significantly different to controls but was distributed more evenly throughout the defect. Bone matrix was now mineralized and trabeculae were thicker than in controls (p = 0.002) indicating faster intramedullary bone maturation. Controls presented extensive periosteal bone formation, major fibrous tissue influx and high vascularization. After 12 and 24 weeks there was no new bone detectable. There were no severe signs of inflammation at all time points.

CONCLUSION

The substitute showed an early induction of bone formation. It promoted accelerated intramedullary bone repair and maturation and prevented periosteal bone formation indicating its potential use for reconstructive surgery of bone defects.

Novel composite implant in craniofacial bone reconstruction

Bioactive glass (BAG) and polymethyl methacrylate (PMMA) have been used in clinical applications. Antimicrobial BAG has the ability to attach chemically to surrounding bone, but it is not possible to bend, drill or shape BAG during the operation. PMMA has advantages in terms of shaping during the operation, but it does not attach chemically to the bone and is an exothermic material. To increase the usefulness of BAG and PMMA in skull bone defect reconstructions, a new composite implant containing BAG and PMMA in craniofacial reconstructions is presented. Three patients had pre-existing large defects in the calvarial and one in the midface area. An additive manufacturing (AM) model was used preoperatively for treatment planning and custom-made implant production. The trunk of the PMMA implant was coated with BAG granules. Clinical and radiological follow-up was performed postoperatively at 1 week, and 3, 6 and 12 months, and thereafter annually up to 5 years. Computer tomography (CT) and positron emission tomography (PET-CT) were performed at 12 and 24 months postoperatively. Uneventful clinical recovery with good esthetic and functional outcome was seen. CT and PET-CT findings supported good clinical outcome. The BAG-PMMA implant seems to be a promising craniofacial reconstruction alternative. However, more clinical experience is needed.

Anchoring of methylmethacrylate filler to the calvarium--technical note

Implanted methylmethacrylate may be unexpectedly displaced due to poor adherence to the bone. We developed a simple technique to fix the material plugging the burr holes for use primarily in cosmetically important areas. At the closure of craniotomy, 2-3 small drill holes are made at the rim of the craniotomy burr hole. To address cranial defects in the pterional region, small holes are placed on the bone surface around the key burr hole. The holes extend into the diploic layer and have no parallel relationship. After fixation of the bone flap, a methylmethacrylate filler mixture is manually plugged into the burr hole and pushed into the small holes, thereby forming horns for secure fixation. None among over 100 patients developed an objectionable bulge attributable to displacement of the filler. Our technique requires no special instruments or materials and decreases the risk of cosmetic problems.

Functional and aesthetic reconstruction of extensive oral ablative defects using temporalis muscle flap: a case report and a sort review

PURPOSE

Temporalis muscle flap (TMF) provides a reliable solution in reconstruction of extensive intraoral ablative defects, providing a valuable alternative to more complex and extensive reconstructive procedures, combining excellent functional and aesthetic rehabilitation with minimal complications. In this article is described in detail the TMF surgical technique with attention to specific methods useful for preventing facial nerve injury and donor-site deformity.

MATERIALS AND METHODS

It is presented the case of a patient with malignant tumour in the region of the upper jaw, palate and inferior half of the nasal cavity, who underwent extensive surgical excision and the resultant defect was successfully reconstructed with TMF.

RESULTS

The reconstructive procedure resulted in excellent immediate and long-term functional (aspiration, feeding and speech) and aesthetic results. During the 5-year follow-up period no complications associated with the flap or the temporal implant, used for donor-site reconstruction were encountered and no local recurrence or tumour metastasis was observed.

CONCLUSION

The TMF is a reliable, technically easy and anatomically sound technique, which combines excellent aesthetic and functional results with minimal complications, if performed correctly.

Temperature elevation during simulated polymethylmethacrylate (PMMA) cranioplasty in a cadaver model

The aims of this study were to: (i) obtain temperature measurements during in vitro polymerisation of polymethylmethacrylate (PMMA) disks of a range of thicknesses; and (ii) obtain tissue temperature measurements at various locations within a skull defect during a simulated PMMA cranioplasty procedure using a cadaver. In vitro, higher temperatures were recorded with increasing PMMA thickness. During the simulated cranioplasty, the maximum temperature was observed inside the PMMA sample, with nearby tissues being exposed to temperatures of greater than 50 degrees C over prolonged periods. There is conflicting information in the literature concerning the sensitivity of brain tissue and bone to elevated temperatures. Preoperatively fabricated PMMA cranioplasty prostheses are recommended.

Evaluation of polymethylmethacrylate adhesion: a comparison of direct onlay versus screw anchoring techniques

Polymethylmethacrylate (PMMA) is still the most frequently used alloplastic material for calvarial reconstruction, especially when dealing with large bony defects. It is strong, provides good protection to the underlying cerebral structures, and is stable and minimally reactive. One of the disadvantages of this material is its tendency to become loose over time because of its poor adherence to bone. Onlay miniscrews in improving PMMA's adhesion to bone have been previously proposed. A series of experiments were conducted to evaluate whether placement of screw anchors will significantly improve the adhesion force between the polymer and bony surface.

METHODS

Four fresh-frozen cadaver heads were used for this experiment. The PMMA preparation and setup time strictly followed manufacturer guidelines. Two experimental groups were created: (1) PMMA was placed on the subperiosteal bony surface with increasing surface areas (areas: 1-20 cm2), and (2) a standard area of 16 cm2 PMMA was placed on the bony surface with an increasing number of titanium miniscrews (number of screws: 0-5). The force required to separate the material from the underlying bone was assessed using a digital pull force gauge (Imada DPS-44) through vertical traction. The experiments were undertaken in triplicate; the results were statistically analyzed using Student t test.

RESULTS

Experiment 1: increasing forces were required as the surface area of PMMA application increased (1.2-42.3 N). The most consistent measurements with a low SD were obtained on the 16-cm2 implant, which was chosen for experiment 2. A 16-cm2 area would allow for the placement of up to 5 screws without technical difficulty. Experiment 2: higher forces were needed to detach the material, with increasing screw placement (1, 79; 2, 132.5; 3, 194.2; and 4 and 5, >196.1 N). In 73 of 75 experiments, the screws remained attached to the PMMA after separation. When the PMMA alone on a 16-cm2 surface area was compared with the placement of one or more screws, the force of adhesion significantly increased for all groups (P < 0.01). There was a 2.6x increase in this force with 1 screw, 4.4x with 2, 6.4x with 3, and 6.5x with 4 or more screws. Three or more miniscrews provided sufficient stabilization to anchor an implant firmly in place while resisting large traction forces.

CONCLUSION

Although greater surface areas of PMMA will increase the adhesion force between the polymer and bone, a clinically and statistically significant increase in this force may only be achieved with the use of miniscrews.

Polymethylmethacrylate for managing frontal bone deformities

The correction of bony frontal deformities has been accomplished with a variety of autogenous and alloplastic materials. Of the various materials currently available, polymethylmethacrylate (PMMA), a valuable biomaterial, has proved to be effective in reconstructing deformities of the frontal bone. The authors present one case of acquired frontal bone deformity reconstructed by subperiostal application of PMMA through a minimally invasive coronal approach. Our preliminary experience with this method has been promising.

Reduction of the potential for thermal damage during hip resurfacing

Resurfacing arthroplasty of the hip is being used increasingly as an alternative to total hip replacement, especially for young active patients. There is concern about necrosis of the femoral head after resurfacing which can result in fracture and loosening. Most systems use a cemented femoral component, with the potential for thermal necrosis of the cancellous bone of the reamed femoral head. We used thermal probes to record temperatures close to the cement-bone interface during resurfacing arthroplasty.

The maximum temperature recorded at the cement-bone interface in four cases was approximately 68°C which was higher than that reported to kill osteocytes. A modified surgical technique using insertion of a suction cannula into the lesser trochanter, generous pulsed lavage and early reduction of the joint significantly reduced the maximum recorded cancellous bone temperature to approximately 36°C in five cases (p = 0.014).

We recommend the modified technique since it significantly reduces temperatures at the cement-bone interface.

The use of temporal polyethylene implant after temporalis myofascial flap transposition: clinical and radiographic results from its use in 21 patients

PURPOSE

The use of temporalis myofascial flap (TMF) as a pedicled flap in craniofacial reconstructive surgery is well established. The transposition of temporalis muscle results in a large hollowing of the temporal fossa that leaves the patient with a cosmetic impairment. Reconstruction of this donor site deformity is desirable. One of the established reconstructive techniques is the use of a prefabricated porous high-density polyethylene (HDPE) temporal implant. In order to evaluate results from its use, we retrospectively reviewed a series of 21 consecutive patients.

MATERIALS AND METHODS

From October 1999 to October 2004, 21 patients (7 men and 14 women) aged 32 to 85 years (mean, 65) had their surgical defects reconstructed with the use of a TMF. The majority of patients (15 of 21) had squamous cell carcinoma of the maxilla or the maxillary sinus. In 17 patients, the reconstructive procedure was performed simultaneously with the oncological resection, whereas in 4, a secondary reconstruction was performed. In 1 patient, bilateral TMFs were used to cover a total maxillectomy defect. Standard surgical approach was used in all patients during TMF elevation. The temporal defect was reconstructed with the use of a prefabricated sterile HDPE implant (Medpor; Porex Surgical Inc, College Park, GA). Fixation of the implant to the recipient infratemporal fossa was performed with black silk sutures (in 2 patients) or titanium miniscrews (in 19 patients). The manufacturer's instructions for the placement of the implant were followed in all cases. One of the 21 operated patients preoperatively received radiotherapy (RT). Of the remaining 20 patients, 5 underwent postoperative RT.

RESULTS

Eighteen patients are alive and free from disease. One died during the perioperative period from myocardial infarction and 2 more from locoregional recurrence of their disease, 18 and 27 months postoperatively. In all 21 patients, the placement of the Medpor temporal implant was successful and no immediate or perioperative complications resulting from its use were encountered, giving an overall success implantation rate of 100%. Follow-up ranged from 9 to 70 months (mean, 39). The condition of the implant was evaluated with computed tomography in 18 of the 21 patients as part of the standard postoperative assessment. Radiographic results of the recipient site did not reveal any abnormalities. In 7 patients, the contour of the HDPE implant could be manually palpated, and in 3, it could be seen to protrude subcutaneously. Esthetic results were judged satisfactory from all patients. The hemicoronal skin flap healed uneventfully in all patients and did not cause a visible scar even to bald male patients.

CONCLUSIONS

The reconstruction of the temporal defect after TMF transposition with the use of a Medpor temporal implant is an easy and safe method. The implant does not seem to cause any tissue reaction, and long-term functional and esthetic results are excellent. When properly used and the relevant manufacturers' instructions are carefully followed, the success rate of the method is extremely high.

A cell encapsulation device for studying soluble factor release from cells transplanted in the rat brain

The transplantation of a variety of naturally occurring and genetically modified cell types has been shown to be an effective experimental method to achieve sustained delivery of therapeutic molecules to specific target areas in the brain. To acquire a better understanding of dosing, implant mechanism of action, and how certain cell types affect remodeling of central nervous system (CNS) tissue, a refillable cell encapsulation device was developed for introducing cells into the brain while keeping them physically isolated from contact with brain tissue with a semipermeable membrane. The stereotactically placed device consists of a hollow fiber membrane (HFM), a polyurethane grommet with watertight cap that snaps into a precisely drilled hole in the rat skull, and a removable cell-containing insert. The cell-containing insert can be introduced or removed in a time-dependent manner to study the influence of soluble factors released from transplanted cells. The study describes the device design and validates its utility using a well-established cell transplantation model of Parkinson's disease.

The Fate of Hydroxyapatite Cement Used for Cranial Contouring: Histological Evaluation of a Case

Craniofacial contouring is a commonly performed procedure applied for traumatic and postsurgical cranial vault or facial skeleton irregularities. Hydroxyapatite cement is an alloplastic material composed of tetracalcium phospate and dicalcium phospate anhydrous that transforms into a paste-like substance when these two compounds placed in an aqueous environment. This mixture, which is a nonceramic microporous calcium phosphate combination, is another alternative for refining the craniofacial contour. There are not enough data regarding bone formation within this material after its use in human beings, however. A case requiring secondary craniofacial contouring after a motor vehicle accident is presented. Hydroxyapatite cement was used for reconstruction, and a second look was carried out for further correction during which secondary contouring of the cement was made and a sample of the previously implanted material was histologically evaluated. It was observed in this case that hydroxyapatite cement is incorporated within the surrounding bony structures and permits secondary contouring procedures. New bone and vessel formation was also detected within the implanted material, but this was limited and thus was not convincing for significant osteoconversion as seen in animal studies.

Glenoid cementing may generate sufficient heat to endanger the surrounding bone

Glenoid loosening is a common complication of shoulder arthroplasty. One possible cause is bone necrosis from the exothermic reaction of polymethylmethacrylate. The relationship between the amount of cement used in glenoid fixation and the risk of thermal injury to bone was examined. Glenoid arthroplasty was done on 17 fresh cadaver scapulas, recording the amount of cement used. The bone surface temperature during cement curing was measured using infrared thermography. Using these data and published thresholds for thermal necrosis, the frontal plane area of bone that would be at risk for necrosis in vivo was estimated. The average weight of cement implanted was 5.35 g (2.65-8.08 g). The maximum temperature recorded averaged 64.7 degree C (48.2 degree-76.8 degree C). The area of bone at risk correlated with the amount of cement used. This study indicates that potentially dangerous amounts of heat may be generated during cementing of glenoid components.

Effects of stem design and pre-cooling prostheses on the heat generated by bone cement in an in vitro model

The necrotizing effects of the heat, particularly at more than 50 degrees C, produced by the exothermic polymerization process associated with the acrylic implant cement polymethylmethacrylate (PMMA) are well documented. The temperature changes that occur are dependent on the thickness of the PMMA. The current study investigates the hypothesis that the heat produced by the bone cement may be reduced by the choice of stem design and by pre-cooling the hip prosthesis. The thermal alterations at the bone-cement interface were measured in an in vitro model. The results indicated that a temperature decrease of approximately 7 degrees C could be achieved by pre-cooling the prosthesis, and by changing the shape of the prosthesis stem from flat and wide to round.