Stability analysis of craniovertebral junction fixation techniques

BACKGROUND

Craniovertebral arthrodesis in the upper cervical spine is challenging because of the high degree of mobility afforded by this region. A novel method for achieving atlantoaxial fixation with use of polyaxial screws inserted bilaterally into the lateral masses of C1 and transpedicularly into C2 with longitudinal rod connection has recently been introduced. The question remains as to whether this technique provides adequate stability when extended cephalad to include the occiput. The purpose of this study was to determine the primary stability afforded by this novel construct and compare its stability with the current standard of bilateral longitudinal plates combined with C1-C2 transarticular screws.

METHODS

We used ten fresh-frozen human cadaveric cervical spines (C0-C4). Pure moment loads were applied to the occiput, and C4 was constrained during the testing protocol. We evaluated four conditions: (1) intact, (2) destabilized by means of complete odontoidectomy, (3) stabilization with longitudinal plates with C1-C2 transarticular screw fixation, and (4) stabilization with a posterior rod system with C1 lateral mass screws and C2 pedicle screws. Rigid-body three-dimensional rotations were detected by stereophotogrammetry by means of a three-camera system with use of marker triads. The range of motion data (C0-C2) for each fixation scenario was calculated, and a statistical analysis was performed.

RESULTS

Destabilization of the specimen significantly increased C0-C2 motion in both flexion-extension and lateral bending (p < 0.05). Both fixation constructs significantly reduced motion in the destabilized spine by over 90% for all motions tested (p < 0.05). No significant differences were detected between the two constructs in any of the three rotational planes.

CONCLUSIONS

Both hardware systems provide equivalent construct stability in the immediate postoperative period when it is critical for the eventual success of a craniovertebral arthrodesis. On the basis of this work, we believe that the decision to use either construct should be determined by clinical rather than biomechanical concerns.

Posterior olecranon plating: biomechanical and clinical evaluation of a new operative technique

The purpose of this investigation was to compare the biomechanical analysis of a new plating technique for olecranon fractures to tension band wiring, and review early clinical results. Six matched pairs of cadaveric ulnae were used for the biomechanical analysis. A transverse osteotomy of the mid part of the olecranon was made. One ulna of each pair was stabilized using a tension band and the other with a posterior hook plate. The ulnae were mounted and loaded, and displacement at the osteotomy site recorded. Twenty patients treated with this new technique (14 fractures and 6 osteotomies) were reviewed at one year (range: 8 to 18 months) for infection, union rate, hardware related complaints. and removal. Statistical analysis showed significantly less displacement occurred at the osteotomy site in the plating group. Clinically, all patients had fracture union, and there were no hardware related problems. Posterior plating with this technique achieves greater stability compared to tension band wiring. Early clinical results indicate a low level of hardware related complications.

Reattachment of the ununited greater trochanter following total hip arthroplasty. The use of a trochanteric claw plate

BACKGROUND

The purpose of this retrospective study was to analyze the utility of a trochanteric claw plate in the treatment of an ununited greater trochanter following total hip arthroplasty.

METHODS

From 1986 through 1999, seventy-two consecutive procedures to reattach an ununited greater trochanter were performed in seventy-one patients. The average age at the time of the index arthroplasty was 66.2 years. The arthroplasty that resulted in the nonunion of the greater trochanter was primary in fifty-four hips, a first revision in sixteen hips, and a second and third revision in one hip each. The mean duration between the hip replacement and the treatment of the nonunion was 8.1 months. The greater trochanter was fixed with the trochanteric plate alone in forty-eight hips and with the plate in conjunction with vertical wires in the remaining twenty-four hips. The average duration of follow-up was 5.1 years.

RESULTS

Osseous union occurred in fifty-one of the seventy-two hips. There was a persistent nonunion in twelve hips and fibrous consolidation in the remaining nine hips. The mean time to osseous consolidation was 3.7 +/- 2.1 months (range, two to twelve months). The mean Merle d'Aubigné hip score was 16.1 +/- 2.4 points at the time of the latest follow-up. A highly significant improvement in function was achieved only in the group with osseous consolidation (p < 0.0001). The highest rate of osseous union was achieved when vertical wires had been used in conjunction with the claw plate. Union occurred in twenty-one of the twenty-four hips in that group (p = 0.025).

CONCLUSIONS

Nonunion of the greater trochanter following total hip arthroplasty can be successfully treated with a trochanteric claw plate. The use of adjunctive vertical wires results in better osseous contact and union.

Mechanical performance of the new posterior spinal implant: effect of materials, connecting plate, and pedicle screw design

STUDY DESIGN

A newly designed spinal implant was tested to evaluate multicycle stiffness and fatigue resistance.

OBJECTIVES

To investigate the effect of different materials, connecting plate, and pedicle screw design on the mechanical performance of the spinal implant.

SUMMARY OF THE BACKGROUND DATA

The addition of cross-linkages did not significantly increase implant compression/flexion stiffness, but accelerated fatigue failure at the rod junctions. Both Ti-6Al-4V spinal implants and the 316L stainless-steel counterparts have been used extensively for clinical cases; however, design factors establishing the proposed superiority of the Ti-6Al-4V implant for fatigue resistance have not, as yet, been extensively studied.

METHODS

Twenty implants with connecting plates (two materials by two screw designs by five implants) and five implants without connecting plates were assembled to UHMWPE blocks and cyclically loaded from 60 N to 600 N at a frequency of 5 Hz.

RESULTS

Failure sites for the tested prototypes were at the cephalic screw hubs or rod-plate junctions. All Ti-6Al-4V implants demonstrated reduced stiffness compared to the structurally identical 316L analogs. The use of connecting plates raised the stiffness of the 316L prototypes without cross-links. However, elimination of the connecting plate avoided stress concentration at the rod/plate junctions and increased fatigue life. The Ti-6Al-4V new system with the minimal notch effect at the screw hubs achieved greater fatigue resistance than its 316L counterpart. By contrast, enlargement of the inner-hub diameter resulted in greater gains for fatigue resistance than for stiffness, especially for Ti-6Al-4V variants.

CONCLUSIONS

Although Ti-6Al-4V was superior to 316L for endurance-limit properties, structural design of the Ti-6Al-4V implant dramatically affects fatigue resistance. This may explain the differences between existing studies and the current report, comparing fatigue life for implants made from these two materials. Our results reveal that Ti-6Al-4V must be carefully treated because of sensitivity to notch, with special consideration given to screw-hub design.

Análise de falhas de implantes cirúrgicos no Brasil: a necessidade de uma regulamentação adequada

Este artigo apresenta alguns casos de análise metalúrgica de falhas de implantes cirúrgicos metálicos utilizados no Brasil. Investigaram-se as causas das falhas de duas placas de compressão de aço inoxidável, uma placa-lâmina de aço inoxidável, uma placa de reconstrução de maxilar de liga de Ti com 6% de alumínio e 4% de vanádio (Ti-6Al-4V) e cinco arames de Nitinol (liga níquel-titânio). Adicionalmente, investigou-se a conformidade destes materiais às especificações técnicas da norma ABNT (Associação Brasileira de Normas Técnica). A investigação revelou que todos os implantes analisados não estavam de acordo com os requisitos mínimos da ABNT/ISO, e que as fraturas prematuras ocorreram por mecanismos assistidos por corrosão e/ou pela presença de defeitos (de fabricação, montagem ou de manuseio). Dados de literatura indicam que implantes de materiais não biocompatíveis podem causar diversos tipos de reações adversas no corpo humano, além de promover a falha prematura do componente e causar danos para o paciente e prejuízos para o investimento público. Não há no Brasil legislação sanitária que tornem compulsórios os procedimentos de notificação e de investigação dos casos de falhas de implantes cirúrgicos.

[Utilization of a porous alumina ceramic spacer in tibial valgus open-wedge osteotomy: fifty cases at 16 months mean follow-up]

PURPOSE OF THE STUDY

The aim of this work was to study the behavior of an inert porous alumina ceramic spacer used with a plate fixation for open-wedge tibial valgus osteotomy in patients with osteoarthritis of the knee and genu varum.

MATERIAL AND METHODS

The population included 50 patients who underwent surgery between October 1994 and December 2000. There were 31 women and 19 men, mean age 55 years at surgery (26 right knees and 24 left knees). Patients were reviewed at 3 weeks, 6 weeks, 3 months, 6 months, and one year, then every 2 years. Clinical and radiological data were available for all patients.

RESULTS

Mean follow-up was 16 months. Two patients were lost to follow-up at 5 and 6 months. The results of the open-wedge tibial osteotomy were in agreement with the usual outcome reported in the literature concerning pain relief, functional recovery, joint motion, angle correction, and good preservation of the clinical and radiological result. Three fracture lines were observed on the lateral tibial plateau but did not affect final outcome or angle correction. There was however one case with loss of correction due to fracture of the screws. Radiographically, at 6 months, there were 9 thin lucent lines around the spacer (24%) which did not affect final outcome. Bone healing was achieved at 3 months on the average in all cases except 2 (4%) where healing was achieved at 8 and 13 months.

DISCUSSION

The porous alumine spacer is a reliable biocompatible and mechanically stable element helpful for achieving bone healing. Integration into bone tissue was radiographically satisfactory. There were no specific complications related to use of the spacer.

Biomechanical evaluation of fixation of posterior acetabular wall fractures

Reproducible fractures of the posterior wall of the acetabulum were created in 10 paired hemipelves from fresh human cadavers. Under anterior-to-posterior loading by a Materials Testing System machine, the load to failure of fixation of the acetabular fractures treated with steel pelvic reconstruction plates and steel screws was significantly higher than that of fixation with titanium ribbons and titanium screws. Forces as little as 725 newtons applied directly to the fragment caused fixation failure; even the most secure form of fixation failed when a relatively small force of 2,123 newtons was applied. These results emphasize the importance of appropriate postoperative measures, such as limitation of hip flexion and restricted weightbearing, to minimize the force directed against the posterior wall until the fracture has healed. Secure fixation of fractures of the posterior wall of the acetabulum is critical, since loss of fixation results in instability and joint incongruity, which limit the options for reconstruction.

Intertarsal and tarsometatarsal arthrodesis using 2.0/2.7-mm or 2.7/3.5-mm hybrid dynamic compression plates

Proximal intertarsal or tarsometatarsal arthrodesis was performed in four dogs using either 2.0/2.7-mm or 2.7/3.5-mm hybrid dynamic compression plates. Mean radiographic follow-up time was 30.5 weeks (range, 15 to 60 weeks). Mean owner follow-up time was 40.5 weeks (range, 27 to 60 weeks). All cases went on to form stable, healed arthrodeses. Owners reported no noticeable lameness problems long term. Complications occurred in one case and included pressure sores and fracture of the calcaneus. Implant failure did not occur in any case.

Evolution of minimally invasive plate osteosynthesis (MIPO) in the femur

Problems with conventional open reduction and internal plate fixation of distal femoral fractures are well established. These problems have been associated with extensile exposures of the fracture site. "Biological plating", like intramedullary nail fixation, of distal femoral fractures preserves the soft tissues about the fracture, and is associated with early fracture consolidation and low rates of infection. Anatomical restoration of the articular surface continues to be the main goal in the treatment of these fractures regardless of the stabilization technique. Submuscular plating techniques, which provide for closed reduction of the diaphyseal/metaphyseal component of the fracture, have improved significantly.

Fixation of distal femoral fractures above total knee arthroplasty utilizing the Less Invasive Stabilization System (L.I.S.S.)

Supracondylar femoral fractures above total knee arthroplasty remain a treatment challenge. Complication rates as high as 30% are associated with both nonoperative and operative treatment. Conventional plate fixation and rigid intramedullary nail fixation has improved the treatment of these fractures. However, problems still exist in the setting of a short distal femoral block and/or significant osteoporosis. Less Invasive Stabilization System (L.I.S.S.) fixation has been utilized for the treatment of supracondylar femoral fractures above total knee arthroplasty. Multiple fixed angle screws give optimal fixation around the femoral component. Advantages appear to include maintenance of distal femoral fixation, low infection, and low need for bone grafting.

Distal femoral fractures: current treatment, results and problems

The evolution of treatment for supracondylar femoral fractures has sequentially addressed the difficulties of alignment, articular reduction, stabilization and fracture union. Adequate surgical stabilization and early motion diminished stiffness, while newer indirect techniques in handling periarticular tissues have greatly improved union rates. Indirect methods of reduction require an understanding of anatomy and deformity to avoid malalignment. The problems we currently face are fixation in osteoporotic bone or small distal articular segments.

Distal femoral fractures and LISS stabilization

In recent years, the technique of surgical stabilization in the distal femur has changed. This change decreased the number of non unions and the need for bone grafting. Minimally invasive surgical techniques with a submuscular plate placement have replaced the emphasis on anatomical reduction in the shaft area. Reconstruction of complex articular injuries has been simplified by more direct visualization of the articular surface with the lateral peripatellar approach. Problems remaining are surgical technique and implant considerations. The Less Invasive Stabilization System (LISS) simplifies the surgical technique for percutaneous plate osteosynthesis. An insertion guide is used to insert monocortical, self-tapping screws through a stab incision. A thread in the plate provides the angular stability for the anchoring of these screws. In extra-articular fractures and simple intra-articular fractures, the distal femoral nail permits intramedullary stabilization. A spiral blade improves fixation of the distal femoral condylar block. Despite the enhanced surgical technique and implant possibilities, a great number of patients show a functional deficiency. These are particularly patients with complex intra-articular fractures. The 'fatigue failure' of the osteoporotic implant-bone construct is a problem in elderly patients. The LISS represents a good option to avoid the addition of bone cement to an osteosynthesis.

Minimally invasive fracture stabilization of distal femoral fractures with the LISS: a prospective multicenter study. Results of a clinical study with special emphasis on difficult cases

The LISS-DF (Less invasive stabilization system-distal femur) is a new type of implant system for the treatment of distal femoral fractures according to the principles of "Minimally Invasive Surgery". A plate, pre-contoured to the anatomy, is inserted through a minimally invasive incision into the epiperiosteal space by means of an aiming device after indirect, closed fracture reduction. The implant is stabilized by insertion of screws which lock into the plate holes and prevent tilting. This is performed with the aid of an aiming device and through stab incisions. It is not necessary for a large area to be exposed at the fracture site. As part of an AO prospective multicenter study, the new system was applied to 112 patients with 116 fractures. The time to follow-up was on average 13.7 months (minimum 7 months, maximum 33 months). Fractures treated were distal femoral shaft and supracondylar femoral fractures. Eight patients died during the study of causes unrelated to the implant. Of the remaining 104 patients with 107 fractures, 96 patients with 99 fractures were available for complete follow-up (93% follow-up rate). In 90% of all cases treated and followed up, the fracture had consolidated during the period of observation. Twenty-three revision operations were necessary in 21 patients. In two cases, implant failure occurred as the result of a pseudarthrosis. The complications can be attributed in nearly all cases to the severity of the trauma and/or a lack of experience when applying the new style implant to a wider range of indications. The results of the study show that with a sound knowledge of the operative technique and careful preoperative planning this system represents an excellent, safe procedure for the treatment of almost all distal femoral fracture types including periprosthetic fractures of the distal femur. There is generally no need for primary cancellous bone grafting.

Immediate mobilization following fixation of mandible fractures: a prospective, randomized study

OBJECTIVES

To compare outcomes of open reduction and internal fixation of displaced mandible fractures followed by either immediate mobilization or 2 weeks of mandibular-maxillary fixation.

STUDY DESIGN

A prospective, randomized, single-blinded study was performed.

METHODS

The study was performed between January 1, 1997, and March 30, 2000. Inclusion criteria were displaced fractures between the mandibular angles, age greater than 16 years, and no involvement of the alveolus, ramus, condyles, or maxilla. All fractures were repaired by means of open reduction and internal fixation using 2.0-mm titanium plates secured either in transoral fashion or percutaneously. Data were collected at 6-week and 3- and 6-month postoperative examinations. Variables were assessed by a surgeon blinded to the history of immobilization and included pain, malunion or nonunion, occlusion, trismus, wound status, infection rates, dental hygiene, and weight loss. Twenty-nine consecutive patients were enrolled, 16 patients to immediate function and 13 patients to 2 weeks of mandibular-maxillary fixation.

RESULTS

No statistically significant differences were found between groups for any of the variables. Immediate release and temporary immobilization showed mean weight loss of 10 and 8 pounds and trismus of 4.2 and 4.6 cm, respectively. One wound separation and one infection were seen in the immobilization population, and no wound separation or infection was seen in the immediate-release group. Dental hygiene was similar between the groups. No malunion or nonunion was noted in either group.

CONCLUSIONS

In this prospective and randomized study, no significant differences were noted between the groups receiving either immediate release or 2 weeks of mandibular-maxillary fixation. The findings support the treatment of selective mandible fractures with 2.0-mm miniplates and immediate mobilization.

First metatarsophalangeal joint arthrodesis: quantitative mechanical testing of six-hole dorsal plate versus crossed screw fixation in cadaveric specimens

Quantitative strength analysis of first metatarsophalangeal joint arthrodesis was performed using two fixation techniques: a small 6-hole plate with an interfragmentary screw or two crossed lag screws. Twelve matched-pair fresh-frozen cadaveric specimens (24 trials) were used for direct comparison of each of the two fixation techniques. All joint surfaces were prepared with power conical reamers utilizing a standard technique. The fixation construct was stressed to failure on each specimen using a computer-integrated materials tester. Fixation stiffness defined as force (load) over displacement and point of ultimate failure was evaluated. The six-hole plate and interfragmentary screw fixation method was a statistically stiffer form of fixation (p > .01) and displayed a greater point of ultimate failure (p > .002) under the laboratory conditions.

[Unstable fracture of the distal radius and its treatment: comparison of three techniques: external fixation, intramedullary pinning and AO plates]

This retrospective study compares 94 distal radius fractures. Sixty one women (median age 66) and 33 men (median age 42) were reviewed clinically and radiologically by a surgeon not involved in treatment. Fractures were classified into three AO groups. Standard X-rays were used for radiological evaluation. Fractures of the distal ulna were evaluated separately. Chi-square tests, Wilcoxon, Mann-Whitney and Fisher's tests were used for statistical evaluation. Women presented mainly "A" type fractures. They were treated by intramedullary pinning. Forty two fractures were grafted, using autogenous bone for young patients and bone substitute for the elderly. Twelve scapholunate dissociations were recorded, all but one were detected in women, 50 years of age or more. Four were painfree, two presented climatic pain and six claimed pain during effort; none had snapping. Radio-ulnar laxity was similar with or without styloid fractures. External fixator and autogenous grafts appeared the most efficient technique for maintaining radial length. Ulnar head fractures were related to a significant higher incidence of sympathetic dystrophy with reduced prono-supination, a correlation not previously noted to your knowledge. This suggests that radius and ulnar head fracture should be classified independently. The amount of pain was not related to classification, internal fixation or gender.

Biomechanical evaluation of occipitocervical fixation devices

Human cadaveric occipitocervical specimens were implanted with three types of instrumentation. The devices were tested biomechanically under three modes of loading to determine the stiffness of spinal constructs and the failure mechanisms of the constructs under extreme flexion. The devices tested were the AXIS Fixation System (with custom plate), the Y-Plate, and the Luque rectangle. No significant differences in stiffness among the devices were found under compression and flexion. The stiffnesses of the plate systems were statistically higher than the Luque rectangle in extension and torsion. In extreme flexion, the plate systems failed by fracture of the C2 pedicles. Modern plate systems, for occipitocervical fixation, provide more stiffness and stability than traditional wiring techniques. This study provides surgeons with information on the relative merits of modern plate and screw systems compared with traditional rod and wire constructs.

Transarticular screw fixation for atlanto-occipital dislocation

STUDY DESIGN

A case report of traumatic atlanto-occipital dislocation managed by transarticular screw fixation.

OBJECTIVES

To present a case with initial failed wire fixation but successful reduction and fixation with transarticular screw fixation and occipitocervical plate stabilization.

SUMMARY OF BACKGROUND DATA

Atlanto-occipital dislocation is generally a fatal injury, except when it occurs in children. Management of this injury is difficult because of multidirectional instability and the problems associated with technical stabilization.

METHODS

Intraoperative atlanto-occipital reduction was achieved and maintained by direct C0-C1 transarticular screw fixation. To protect this fixation, a posterior occipitocervical fusion at C0-C2 using a Y-plate was performed.

RESULTS

The internal fixation and reduction were maintained, indicating a good surgical outcome, at examination 2 years after surgery. The initially severe neurologic deficit was reduced to some motor weakness of the right hand and weakness of oculomotor function.

CONCLUSIONS

Anatomic reduction and reliable fixation with transarticular screws may provide satisfactory clinical results with important neurologic recovery in cases of atlanto-occipital dislocation.

RAB-plate versus sliding hip screw for unstable trochanteric hip fractures: stability of the fixation and modes of failure--radiographic analysis of 218 fractures

BACKGROUND

The sliding hip screw has gained considerable acceptance in the treatment of unstable trochanteric fractures. However, the new type of 120 degrees fixed angle blade-plate with a buttress rod (RAB-plate) showed encouraging clinical results. The purpose of this study was to assess stability of fixation and analyze modes of failure in unstable trochanteric hip fractures treated with these devices.

METHODS

A retrospective radiographic review of 218 unstable fractures was performed. Linear and angular displacements of the major fragments and implant migration into the femoral head during healing were assessed. Additionally, adequacy of the reduction and the location of the implant within the femoral head as predictors of fixation failure were evaluated.

RESULTS

The postreduction neck-shaft angle was maintained in the majority of the fractures in both groups. However, there was a significantly higher incidence of varus angulation by 10 degrees or more by the completion of healing among fractures treated with the sliding hip screw (p = 0.04). There was no statistically significant difference in vertical migration of the device into the femoral head between the implants used (p = 0.3). There was a significant relationship between failure of the fixation and varus reduction (p = 0.04) as well as screw/neck angle deviation more than 20 degrees in the lateral projection (p = 0.005) or if the implant was in a superior or posterior position (p = 0.02).

CONCLUSION

The RAB-plate provided a more stable fixation, especially with regard to maintained postoperative alignment. However, positive predictors for fixation failure were identical for both devices. Here, the screw/neck angle deviation has had the strongest significance for prediction of fixation failure.

[Surgical treatment of distal femoral fractures using extra-medullary osteosynthesis]

Forty seven fractures of the distal femur treated by internal fixation using a supracondylar compression screw or blade plate were retrospectively evaluated regarding their radiological and functional results. Blade plates were used for all types of distal femoral fractures until 1992; their indications were subsequently restricted to simple supracondylar fractures whereas a compression screw was preferred for other types of fractures. Taking into account the condition of the patients before fracture, 85% good and very good results were achieved with both techniques. Malunions resulted in poor functional outcomes (50% good and very good results). Malunions were mainly observed in patients with complex fractures (90% of cases with malunion), which confirms the poor prognosis of comminuted fractures. Nonunions (65%) and infection (3%) resulted in poor functional results. The presence of a bony defect in the medial femoral cortex increases the risk of nonunion; bone grafting should be used in such cases. The recent use of a long femoro-femoral external distractor in a few patients has proved of value as it allowed to achieve accurate reduction and considerably eased fracture reduction and fixation.

Plating of femoral shaft fractures. A review of 15 cases

The objective of this study was to define the role, indications and outcome of plating in femur shaft fractures. All femoral shaft fractures admitted and treated by the authors during a 2-year period were analysed. The authors personally treated a total of 135 femur fractures. Of these 135 fractures, 15 (11%) were treated with primary plating. The femoral fractures were classified as grade I (n = 4), grade III (n = 3), grade IV (n = 4), grade V (n = 3), and grade VII (n = 1) (OTA classification). Three patients sustained open fractures (one grade I and two grade II, Gustilo and Anderson classification). Pelvic (6) or ipsilateral lower extremity injuries (4) occurred in 10 of the 15 patients. A total of 23 body areas were injured, most commonly the chest (n = 10), abdomen (n = 5), head (n = 6) and blood vessels (n = 3). There were no infections reported. Two implant failures were noted. Femur plating is a useful technique in polytrauma patients for specific indications where intramedullary nailing (IMN) may be contra-indicated or technically not feasible. Although the postoperative morbidity (ARDS, death) in our study seems to be lower after plating than after intramedullary nailing, the rate of complications of fracture healing (30%) is significantly greater with femur plating than with intramedullary nailing (12%).

Plate fixation of prostheses after segmental resection for bone tumours

This study investigated the concept of using plates to attach endoprostheses to bone after segmental resection for bone tumours in an animal model. Titanium alloy plates integrated with the prosthesis and coated with hydroxyapatite were attached to bone by screws. This type of uncemented fixation relied on the induction of periosteal bone formation into and around the plates to secure the implant to bone. Two, three, and six-slotted plate designs were investigated. On retrieval, each plate was securely fixed by new bone. Bone apposition on the external surface of the plates occurred through a combination of periosteal bone production, invasion of bone through slots in the plate, and bone growth over the ends of the plates. Most plates became incorporated into a remodelled cortex. Higher bone turnover rates (microm day(-1)) were seen in bone in the slots of the plate compared with normal cortical bone turnover (p < 0.05). Significantly higher rates of turnover were measured beneath slotted parts of the plates compared with regions below the unslotted parts (p < 0.05). The cross-sectional area of bone surrounding the six-plate implant design was significantly higher than that of the three-plate (p < 0.05) and two-plate (p < 0.05) designs. In addition, significantly more bone formed adjacent to the six-plated implant design compared with that in the contralateral limb (p = 0.002). However, no significant difference was found when the total cortical area around the three-plated design was compared with that of the contralateral limb (p = 0.63). In contrast, significantly less bone was measured adjacent to the two-plate design than in the untreated limb (p = 0.001). Image analysis also demonstrated increased cortical porosity adjacent to the six-plate design compared with the three-plate (p = 0.004) and two-plate (p < 0.05) designs. Finite element analysis demonstrated that the six and three-plate designs increased the second moment of area compared with that in the left tibia (p = 0.003 and 0.066, respectively). However, the attachment of the more flexible two-plate design did not significantly increase the second moment of area compared with that in the contralateral limb (p = 0.235). It was concluded that due to both mechanical and biological effects, the hydroxyapatite-coated plate designs generated new bone that enhanced fixation and encouraged plate integration into the load-bearing structure of the cortex. This method of fixation may be an alternative to the use of intramedullary cemented stems in patients requiring bone tumour implants and may be the only way to preserve the joint in difficult cases where only short segments of bone remain.